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Methodology

How Takt computes

Takt computes from your signs, not from the calendar.

A calendar calculation takes your last period and adds an average. The cycle app Takt reads the values you record instead — temperature, cervical mucus, bleeding — and computes with them in four steps: it confirms what your signs show. It learns how your cycle runs. It places how precisely it can compute. And it finds patterns that are only in your data.

The longer you keep at it, the narrower your window gets

Takt never gives you a date alone. It gives you a date and how wide the window around it lies — and that width is calculated, not felt. At the start, when Takt knows nothing about you yet, it is four days in each direction. After three cycles with little variation it is one.

Figure 1 — window width by data available Four states one below the other on a shared centre line. The centre line is the forecast day, the bar width the margin around it. With no cycle of her own, Takt computes with an average value and draws no window at all. Under three cycles it is minus four to plus four days, that is eight days of uncertainty. From three cycles with a variation of five to thirteen days it is minus two to plus two, that is four days. From three cycles with a variation of up to four days it is minus one to plus one, that is two days. The centre line is the forecast day. The bar width shows how much margin Takt gives around it. Average no cycle of your own no window −4 / +4 under 3 cycles 8 days −2 / +2 from 3 cycles · variation 5–13 days 4 days −1 / +1 from 3 cycles · variation up to 4 days 2 days Lavender = fertile window · 1 day = the same width in every row
Fig. 1 — The levels of uncertainty and the condition under which Takt moves into each. Takt draws a fertile window in three of them: on the average it names the expected period but no window — and for very strongly varying cycles neither of the two (see step 3).
Source: computation rule of the Takt engine. The thresholds are below in step 3.

That is the difference from a forecast with no such statement: you see not only what Takt expects, but where you stand.

The four steps

Step 1 · Result: the evidenced ovulation

Confirming — what your signs show

After ovulation the basal body temperature rises and stays up. That is not a feeling, it is a pattern you can see in a curve. Takt checks this pattern against a fixed rule — and tells you when it holds: probable from your temperature, one sign.

Measured vaginally or rectally, the curve is steadier than orally — all three sites are permitted, but they are not equivalent. Whichever you choose: stay with it within a cycle.

The rule

  • A coverline at the level of the highest of the six preceding low readings
  • Three readings in a row above it
  • The third at least 0.2 °C above the line — otherwise Takt waits for a fourth
  • Takt sets your ovulation to the day before the first raised reading

Rule set: the symptothermal method, studied in 900 women over 17,638 cycles — Frank-Herrmann et al. 2007 (see sources).

Example: what this looks like in a real curve

Your temperature on six days before the rise: 36.35 · 36.40 · 36.30 · 36.45 · 36.35 · 36.40 °C

The highest of these values is 36.45 — that is where your coverline lies. Then comes: 36.60 · 36.65 · 36.70 °C

→ Three readings in a row above the line, the third 0.25 °C above it — more than the 0.2 required. Takt therefore sets your ovulation to the day before the 36.60: probable from your temperature, one sign.

Had the third reading been only 36.55 (0.10 °C above the line), Takt would have waited for a fourth raised reading — the rule is not met yet, and Takt does not pretend otherwise.

Temperature is optional. If you record none, Takt carries on computing as normal — only this one piece of evidence falls away, and Takt does not claim it by proxy.

Takt says openly how firmly a statement stands — three levels, never claiming more than the evidence carries.

The three evidence levels

  • Estimated — no measurement available, computed from your cycle rhythm alone.
  • Probable — the three-over-six rule holds: a strong, but single sign.
  • Double-confirmed — temperature AND your cervical mucus peak agree: the highest evidence level Takt awards for your ovulation.

“Confirmed” belongs to the third level alone. One sign makes your ovulation probable — two confirm it. Takt shows you this level right at the ovulation, not only in the small print.

If you record no cervical mucus, it stays at “probable” — Takt does not claim the double check by proxy.

Step 2 · Result: the date of your period

Learning — how your cycle runs

Takt remembers three values about your cycle: how long it is, how long your period lasts, and how long your luteal phase is — the time between ovulation and the next bleeding.

The last one is the interesting one. It is usually assumed to be 14 days, but it is individual and remarkably stable across cycles. Takt computes it from your evidenced ovulations — from the first one on: as soon as an ovulation is evidenced and the next period has begun, Takt computes with your luteal phase instead of the textbook one. Every further evidenced ovulation steadies the value.

The order of precedence, for each of the three values

  1. Your own setting, if you have made one
  2. The median of your completed cycles
  3. The average value (28-day cycle · 5-day period · 14-day luteal phase)

Median, not average: a single outlying cycle does not shift your values.

Why no fixed standard value: in over 90 % of women the median cycle length lies between 21 and 35 days — Grieger & Norman 2020, around 1.58 million women (see sources).

Example: why the median and not the average

Your last five cycles, sorted by length: 27 · 28 · 28 · 29 · 35 days

→ Median = 28 days — the value in the middle. The average would be 29.4.

That one 35-day cycle — perhaps a stressful week, perhaps a trip — would pull an average up by a day and a half and shift your forecast for good. On the median it has no influence. It stays visible all the same: in step 3 it makes your window wider instead of distorting your date.

Cycles you bring across from another app count towards this in Takt. Anyone who moves with a history does not start from scratch.

Step 3 · Result: your fertile window

Placing — how narrowly Takt computes

Every forecast gets a width, and the width follows a rule, not a gut feeling. Two things decide it: how many completed cycles Takt knows of yours, and how much they vary — the gap between your shortest and your longest of the last six completed cycles.

The five states

The five confidence states and the window width each one produces
StateConditionYour uncertaintyWindow in total
Averageno cycle of your own completed yetaverage values—
Wide windowfewer than 3 cycles−4 / +4 → 8 days15 days
Medium windowfrom 3 cycles, variation 5 to 13 days−2 / +2 → 4 days11 days
Narrow windowfrom 3 cycles, variation up to 4 days−1 / +1 → 2 days9 days
No windowfrom 3 cycles, variation 14 days or more—no day named

The fertile window runs from 5 days before to 1 day after the ovulation point — seven days from biology, plus your uncertainty on both sides; their sum is above.

No window is the only state that draws none: from 14 days of variation onwards, Takt names no ovulation day. A window spanning two weeks of variation covers almost half the cycle — that would not be information, it would be a disguise. If your temperature has evidenced the ovulation in this cycle, that measured window stays visible; the forecast stays silent all the same.

Example: how one more cycle changes the window

Anna has three completed cycles: 27 · 28 · 29 days → variation 2 days
→ Three cycles, variation up to 4 days: narrow window, uncertainty −1 / +1 → 2 days.

Bea also has three cycles, but less settled ones: 24 · 29 · 33 days → variation 9 days
→ Three cycles, but variation between 5 and 13 days: medium window, uncertainty −2 / +2 → 4 days.

Both of them get a date. Anna is also told that it is dependable — Bea is told that hers is less so. It is exactly that second piece of information that is missing wherever only a date stands.

As long as no cycle of your own is complete, Takt computes with the average value and writes that down too. A population value is not uncertain knowledge about you — it is no knowledge about you at all, and Takt does not pretend otherwise.

Takt shows you what the width is made of

A window width as a finished number does not say what you can change. Takt therefore breaks it down — in the app as a sum, with each term named.

What your window is made of

  • Seven days come from biology. Five before it, because sperm can survive up to five days in fertile cervical mucus, the day of ovulation itself and roughly one after it, for as long as the egg can be fertilised. That is why the window reaches much further before ovulation than after it. Those seven never change — for nobody, with no app, however much you measure.
  • The uncertainty comes from your ovulation shifting from cycle to cycle. One to four days on each side, depending on how precisely your ovulation day is known. It is the only part that moves.

A measured window has no uncertainty at all: it comes from cervical mucus and a temperature rise and is not a forecast but an observation. Takt therefore does not break it down, but marks it as a measurement.

That is why “measuring more” helps, and where the limit lies: measuring shrinks the uncertainty — the seven biological days remain.

And it is a calculation, not a judgement. Takt does not tell you whether your window is “good” or “too wide”, and it asks nothing of you.

If your cycles vary a great deal, the window stays wide — and if they vary too much, Takt names no day. That is the honest answer, not an excuse: a narrow window over varying data would be invented.

Step 4 · Result: not a date, but an insight

Finding patterns — what is only in your data

The question that matters day to day is rarely “when is my period coming” — it is “why do I feel like this today”. The why belongs to you and your doctor. The when is in your data, and that is where Takt gets it out: it counts which symptom occurs in which cycle phase for you — over your last six completed cycles, not over everything you have ever recorded.

That is a deliberate decision, not a technical limit: a pattern that stops should disappear again. If Takt counted over your whole history, two hundred old hits would outlive every fresh counter-example — and a statement about your body would still stand long after your body had disproved it. That would hit the woman who has been at it longest, and precisely in the phases in which patterns really do shift.

The thresholds

  • Counting runs over your last 6 completed cycles — the same window Takt uses to measure your variation
  • From 3 entries of the same sign onwards, Takt speaks of a tendency
  • From 75 % of those in the same phase, of a confirmed pattern
  • At most three patterns at a time — the clearest ones
  • As long as no cycle is complete, it stays a tendency: there is no denominator in which anything could have repeated

Not a forecast and not a model, but a tally of your own observations.

What is shown is not how often you recorded something, but in how many of your six cycles it occurred — as a fraction, say 4/6. A number that keeps growing over the years mostly tells you how long you have been using the app. A fraction with a fixed denominator tells you how well the pattern holds.

Example: when an observation becomes a pattern

You have recorded headaches eight times in your last six cycles. Spread across the cycle phases: 7× before the period · 1× otherwise → 88 %

→ Over 75 % in the same phase: confirmed pattern. Takt tells you on the days when you are there again, and shows you alongside it in how many of the six cycles it actually occurred.

Were it 5 out of 8 (63 %), it would stay a tendency — Takt shows it more cautiously and waits to see whether it holds. Under three entries Takt says nothing at all: two hits are chance, not a pattern.

Why a break from tracking is not counter-evidence

Each of the six cycles carries one of three states, not two: hit · recorded and not present · not recorded at all. The third is the important one. Had you simply recorded nothing in one cycle, a gap in your records would otherwise look exactly like a fading pattern — and Takt would put a statement in your mouth that your data does not support. A gap stays a gap.

Takt’s analysis grows with you: first observation, then tendency, then pattern. It stays silent as long as there is nothing there — and it forgets again once there is nothing left.

What comes out at the end: one sheet for the consultation

From the same data Takt produces a doctor’s report as a PDF — not as a screenshot of the app, but in the form that gets read in a practice. It begins with what every gynaecological history asks for: current cycle day, first day of the last period, and what the figures rest on.

It is ordered along the axes of the FIGO system of 2018: cycle length 24–38 days, bleeding duration up to 8 days — plus the variation between your shortest and longest cycle, for which FIGO sets different limits by age. Two details make the difference:

  • Range instead of average. “28 days on average” can come from 27 and 29 or from 21 and 35. The report therefore shows both ends.
  • Restraint in the verdict. “Regular cycle, unremarkable” appears only where all axes lie within the reference range and at least three cycles are on record.

Along with the temperature curve with the coverline drawn in and the full raw record, so that every figure on the sheet can be checked. Your doctor does the interpreting — the report supplies the material for it.

The computing happens on your device

Takt has no backend and no account. The engine runs locally, with no network connection, and it is deterministic: the same inputs always give the same result. There is no learning model whose behaviour shifts unnoticed — the rules on this page are the rules that do the computing.

Your data sits encrypted in the key store of your operating system. Takt does not transmit it — no server sees your values, not even when the doctor’s report is created.

For doctors, midwives and regulators

The full specification — recording parameters, the algorithm verbatim, the evidence base, scope and test procedure. Every threshold matches the shipped state; none of them is simplified here.

Recording parameters and resolution

Basal body temperature 35.0–40.0 °C in 0.05 steps · bleeding in four intensities plus “none” · cervical mucus in 4 levels by quality · cervix in 3 levels (optional, off by default) · resting heart rate 40–160 bpm (optional, off by default) · 15 symptoms, two of them (hot flush, night sweats) with an optional daily level of mild/moderate/severe · free text.

Missing fields are carried as missing, not as a zero value. Intercourse can be recorded but enters no calculation.

The algorithm verbatim

Cycle segmentation — day 1 = bleeding ≥ light, minimum gap 15 days, bleeding duration.

Ovulation confirmation — coverline from six low readings, 3 above it with ≥ 0.2 °C, fallback criterion of a fourth reading, ovulation day, mucus peak, window edges.

Statistics — median cycle length over the entire history, range and variation windowed to the last 6 completed cycles, luteal phase as the median over the evidenced ovulations — with no minimum count, from the first one on.

Forecast — period date, ovulation point, order of precedence, window formulae.

Confidence levels — five: average · wide · medium · narrow · no window from a windowed variation of ≥ 14 days — the one state in which no point is forecast; a window already measured is untouched by this.

Symptom-phase tally — window: the last 6 completed cycles, identical to the variation window; ≥ 3 evidence days, 50–75 % tendency, from 75 % a pattern, max. 3; the day level decides whether a pattern holds, what is shown is the cycle coverage as a fraction with a capped denominator; three states per cycle — hit, recorded and not present, not recorded; with no completed cycle there is no denominator and therefore no confirmation.

Dissenting voices in the guidelines — and the answer to them

Three guideline bodies judge basal body temperature as an instrument for confirming ovulation with reservation or rejection. They stand here verbatim: a specification that leaves out the counter-finding is not a specification.

  • NICE NG257, Fertility problems: assessment and treatment (NICE guideline, published 31 March 2026), recommendation 1.18.9: “Do not use basal body temperature charts to confirm ovulation because they do not reliably predict ovulation.” — marked [2004], carried over unchanged in the 2026 update.
  • Practice Committee of the ASRM, Fertility evaluation of infertile women: a committee opinion, Fertil Steril 116(5), 1255–1265 (2021): “Serial, daily basal body temperature (BBT) testing is an inexpensive, although often unreliable, method of predicting ovarian function.” … “Given the tedious nature of the testing and its lack of accuracy, this test is not routinely recommended today, especially when the menstrual history is consistent with ovulatory cycles.”
  • ESHRE, Evidence-based guideline: Unexplained Infertility (2023): for basal body temperature against ultrasound follicle monitoring as the reference standard, sensitivity 77 %, specificity 33 %, accuracy 74 % (Guermandi et al. 2001, 101 women with regular cycles). Recommendation: tests to confirm ovulation are not routinely indicated where the cycle is regular; where confirmation is indicated, the guideline names the LH urine test, ultrasound and mid-luteal progesterone — not basal body temperature.

The answer, in five points:

  1. The subject is a different one. All three judge basal body temperature as a diagnostic instrument in infertility work-up — as a substitute for ultrasound, an LH test or a progesterone measurement. Takt replaces none of these procedures and enters no work-up: it documents an analysis that the woman using it could carry out herself by the same published rule.
  2. The physiology is not disputed. None of the three bodies contradicts the biphasic course; ASRM 2021 records it expressly (“Ovulatory cycles are generally associated with biphasic BBT recordings”). What is disputed is the reliability as proof, not the pattern.
  3. The reservation applies to confirmation — and that is exactly where Takt’s ladder of levels sits. A temperature rise alone yields the level probable in Takt, not confirmed; “confirmed” is reserved for the double check of temperature and cervical mucus peak. The level words are created at exactly one place in the source (lib/model/evidenz.dart), not afresh on every surface. Two automated guards back this up: a vocabulary test keeps blocked terms out across the entire body of text, and a state-aware check additionally requires an evidenced ovulation for the word “confirmed” — wherever Takt assembles its sentences at runtime. The reservation therefore lands on a statement Takt does not make from one sign.
  4. The sensitivity gap is the reason for a fixed rule. A share of ovulatory cycles shows no clearly biphasic curve — ASRM 2021: “Some ovulatory women cannot document clearly biphasic BBT patterns”; quantified in Moghissi 1976 (Fertil Steril 27(12), 1415–1421) as “approximately 20 % of ovulatory cycles” in 30 women, one cycle each. The consequence in the product: a rule that is not met is not a finding. Takt says “not evidenced yet” and never “no ovulation” — a statement about an ovulation that failed to occur would be a pathological finding and is ruled out.
  5. Takt derives no accuracy claim about itself from any of this. What is given is the computed window width, never a hit rate — and the evidence level a statement stands on.

What does not follow from this: this answer justifies Takt’s choice of words and its evidence levels — not a suitability for contraception and not one for investigating cycle disorders. Takt is intended for neither (see “What Takt is not”). The figures named describe the method in a clinical population, not the product.

Evidence base — implemented and deliberately not implemented

The four load-bearing sources, each with its function, are set out in full under “What the rules rest on”.

Reviewed but not implemented: Shi et al. 2026, Wang et al. 2025 and Thigpen et al. 2025 on wearable sensors. Takt does not implement these methods and therefore relies on none of their figures. Two limitations of this literature come on top: error margins determined retrospectively, and manufacturer funding with LH rather than ultrasound as the reference.

Why Takt names no accuracy figure of its own: there is no prospective validation. What is given is the computed window width, not a hit rate.

Scope and limits of the specification

Confirmation is retrospective · a confirmed ovulation does not anchor the current period date · there is no automatic outlier handling · irregular cycles (Yu et al. 2022: sensitivity 69 % for regular, 21 % for irregular cycles) · no substitute for medical assessment.

Scope of the analysis rule. The symptothermal rule and the statistics derived from it have been studied for cycles in the reproductive normal range without hormonal contraception. For adolescence, perimenopause, postpartum cycles, PCOS, thyroid dysfunction and for cycles under hormonal contraception there is no study of the rule — for perimenopause that is a gap in the evidence, not in the literature search: a quantified study of the symptothermal method in this phase does not exist, and the developers of the method themselves list it as a “special situation” calling for instructor support rather than automatic application of the rule. Takt applies the rule there unchanged and knows no special-case detection. Recording, history and the doctor’s report are untouched by this — they do not presuppose the rule.

What Takt does do in these phases is document and display: record signs and symptoms, show their course, prepare the material for the consultation. Takt does not place anything in a stage, rate a severity or forecast the transition — not because the data is missing, but because that is not the purpose.

Reproducibility and test procedure

A pure function with no randomness, no network, no server-side rule update · personas across the whole span of life · vocabulary test · catalogue of statements · 75 reference vectors against external guidelines (AWMF/Sensiplan, FIGO) · 20 frozen schema versions · a lock against changing the computation logic without a matching update of tests and explanatory text.

This is not a certified QMS under ISO 13485 — for a product outside the MDR, none is envisaged.

The doctor’s report in detail

Header line · FIGO reference ranges with the 2019 corrigendum (cycle length 24–38 d, < 24 frequent / > 38 infrequent · variation ≤ 7 d at 26–41 years, ≤ 9 d at 18–25 and 42–45 years · bleeding duration ≤ 8 d · bleeding intensity qualitative, no mL threshold) · range instead of mean · the logic of the summarising sentence · measurement coverage, time reference (“biphasic · in 4 of 5 cycles”) and the raw record as evidence for every figure.

Age banding. Takt asks for the year of birth and selects the FIGO threshold accordingly (≤ 7 days at 26–41 years, ≤ 9 at 18–25 and 42–45). Without a year of birth the axis is shown but not assessed, rather than testing against the laxer limit. Why a year and not a date is enough is explained by the app in the sheet “Why Takt asks for your year of birth”.

The 2019 corrigendum corrects the swapped categories “frequent”/“infrequent” and the irregularity threshold.

What the rules rest on
  • The symptothermal rule: Frank-Herrmann, P., Heil, J., Gnoth, C., Toledo, E., Baur, S., Pyper, C., Jenetzky, E., Strowitzki, T., Freundl, G. (2007): The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple’s sexual behaviour during the fertile time: a prospective longitudinal study. Human Reproduction 22(5), 1310–1319. DOI: 10.1093/humrep/dem003
  • How real cycle lengths are distributed (descriptive, not a proposed norm): Grieger, J. A., Norman, R. J. (2020): Menstrual Cycle Length and Patterns in a Global Cohort of Women Using a Mobile Phone App: Retrospective Cohort Study. J Med Internet Res 22(6), e17109 — 1,579,819 women; in 91.1 % of them the median cycle length lay between 21 and 35 days. DOI: 10.2196/17109
  • The biphasic temperature pattern: AWMF S2k guideline Nicht-hormonelle Empfängnisverhütung (register no. 015-095, DGGG/OEGGG/SGGG, valid until 31 December 2028), patient version · WHO/Johns Hopkins CCP, Family Planning: A Global Handbook for Providers, ch. 18, p. 300 (a rise of 0.2–0.5 °C after ovulation) · Gnoth, C., Frank-Herrmann, P., Bremme, M., Freundl, G., Godehardt, E. (1996): How do self-observed cycle symptoms correlate with ovulation? Zentralblatt für Gynäkologie 118(12), 650–654 — 87 cycles, validated against ultrasound and an LH test. PMID: 9082700
  • The counter-finding on basal body temperature (verbatim in the specialist section, with the answer): NICE, Fertility problems: assessment and treatment, NICE guideline NG257, published 31 March 2026, recommendation 1.18.9 · Practice Committee of the American Society for Reproductive Medicine (2021): Fertility evaluation of infertile women: a committee opinion. Fertil Steril 116(5), 1255–1265. DOI: 10.1016/j.fertnstert.2021.08.038 · ESHRE Unexplained Infertility Guideline Development Group (2023): Evidence-based guideline: Unexplained Infertility, eshre.eu/guideline/UI · Moghissi, K. S. (1976): Accuracy of basal body temperature for ovulation detection. Fertil Steril 27(12), 1415–1421. PMID: 1001528
  • The clinical reference range of the report (the threshold the report assesses against): Munro, M. G., Critchley, H. O. D., Fraser, I. S.; FIGO Menstrual Disorders Committee (2018): The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. Int J Gynaecol Obstet 143(3), 393–408. DOI: 10.1002/ijgo.12666 — together with the corrigendum: Int J Gynaecol Obstet 144(2), 237. DOI: 10.1002/ijgo.12709

No accuracy figure for Takt stands here: there is no prospective validation, and figures from studies of other devices and methods would say nothing about Takt. Where the specialist section does carry outside figures — the counter-finding on basal body temperature, the figures on irregular cycles — they are cited as a limit of the method, never as a performance of the product. Two of the sources name different ranges because they measure different things: FIGO sets down what counts as clinically normal (24–38 days); Grieger & Norman describe how real cycles are actually distributed (91.1 % at 21–35 days). The report assesses by FIGO.

What Takt is not

  • Not a method of contraception. Takt makes no statement about whether a day is suitable for avoiding pregnancy.
  • Not a diagnostic tool. Takt assesses no illnesses and makes no statements about cycle disorders, PCOS or endometriosis.
  • Not a substitute for medical advice. The report prepares your records for the conversation; it does not replace it.
  • Not a medical device. Takt is software for recording and displaying your own cycle data and pursues no medical purpose within the meaning of Regulation (EU) 2017/745.

Frequently asked questions

Does Takt compute, or does it guess?

Takt computes by fixed rules, and this page sets them out in full. There is no AI model and no black box: the same inputs always give the same result, and every threshold can be looked up.

How does Takt confirm an ovulation?

Retrospectively, from your temperature: a coverline at the level of the highest of the six preceding low readings, three readings in a row above it, the third at least 0.2 °C higher. Takt then calls your ovulation “probable” — from your temperature, a strong but single sign. If your cervical mucus peak fits as well, it becomes “double-confirmed”: the highest evidence level Takt awards. The word “confirmed” stays reserved for that second level.

When does a new cycle begin for Takt?

For Takt a new cycle begins on the first day with bleeding of at least “light” intensity. Spotting is stored and displayed, but it does not shift your cycle calculation.

From when does my window get narrower?

From three completed cycles onwards, Takt computes with your own values instead of average ones. If your cycle lengths lie within four days of each other, your uncertainty shrinks to one day on each side — two days on top of the seven that come from biology. Cycles from another app count towards this.

Why is my fertile window so wide?

Because seven days of it are not negotiable: five before ovulation, because sperm can survive up to five days in fertile cervical mucus, the day of ovulation itself and roughly one after it, for as long as the egg can be fertilised. That is why the window reaches further before ovulation than after it. Those seven are the same for everyone. Everything beyond them is the uncertainty — one to four days on each side, depending on how precisely your ovulation day is known. That is the only part Takt shrinks when you measure.

Why does a pattern Takt has already shown me disappear again?

Because Takt counts over your last six completed cycles, not over your entire history. A pattern that stops should disappear again — otherwise a statement about your body would still stand long after your body had disproved it. A break from tracking does not count as counter-evidence: cycles with no entry are carried as a gap, not as a miss.

What does Takt do if my cycles are irregular?

It keeps the window wide and tells you that it is wide. If 14 days or more lie between your shortest and your longest of the last six cycles, Takt names no ovulation day at all — then “No window” stands there instead of a number. Irregular cycles are the hardest case for any forecasting method; a narrow window would be a claim there, not an achievement. The same holds if your cycle is still settling after a hormonal change: Takt keeps the window wide then too — and draws it tighter as soon as your pattern holds again.

Do I need a thermometer?

No. Without temperature, Takt carries on computing cycle, statistics, forecast and patterns as normal. With temperature, the retrospective ovulation confirmation is added — and your learned luteal phase, which sharpens future forecasts.

Where is my data?

Encrypted on your device. Takt has no account, no backend, and transmits nothing.

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