Period Tracker for Irregular Periods: 6 Apps Compared (2026)
Most apps are built for a 28-day cycle that only 13% of cycles actually follow. These six handle the other 87% with different levels of honesty.
A period tracker for irregular periods needs to do two things most apps skip: keep an honest record when its prediction is wrong, and stop guessing when it does not know. Cycles that run short one month and long the next are common, and they are not usually a sign of a problem, so the goal is a clear history you can read and share, not a red circle on a date the app made up. This guide compares Clue, Flo, Apple Health, Spot On, Euki and Otty on exactly that, then walks through how to track an irregular cycle whichever app you pick.
What is the best period tracker for irregular periods?
The best period tracker for irregular periods is one that separates what you logged from what it guessed, lets you switch the guessing off, and makes the history easy to hand to a doctor. On those three tests Clue comes out ahead for most people, Apple Health wins on price, and Spot On wins for anyone who wants no predictions at all.
That answer changes with what you need from the app. If you want a partner to see the pattern too, Otty is the only one here built for that. If you want a hormone-free birth control method that publishes its own effectiveness with irregular cycles, that is a different category, covered in the FAQ.
Before the app-by-app detail, it helps to know why so many trackers get this wrong, because it is the same reason for all of them.
Why do period trackers get irregular cycles wrong?
Calendar-based trackers get irregular cycles wrong because they predict from your past cycle lengths, and on an irregular cycle the past does not repeat. Nearly all of the variation sits in the first half of the cycle, from the period to ovulation, which is the half a calendar cannot see.
The scale of that variation is bigger than most apps let on. In a 612,613-cycle analysis, only 13% of cycles were the textbook 28 days, and the first half of the cycle ranged from 10 to 30 days while the second half stayed within a tight 7 to 17. The Apple Women’s Health Study found a mean cycle of 28.7 days with a standard deviation of 6.1 days across 165,668 cycles.
So a tracker that was off by a week did not malfunction. It did what every calendar tracker does, which is average your history and hope. The NICHD puts irregular cycles at 14% to 25% of women, which means a large share of every app’s users are being served a prediction the app cannot support. The full picture of what the research found is in our guide to how accurate period tracker apps really are.
An irregular cycle does not need a better prediction. It needs an app that is honest about not having one.
How we compared these apps
Every app was scored on the same five questions. They double as the questions to ask of any tracker you come across later, so keep the list.
One criterion underneath all five is trust in the record itself. An irregular cycle is exactly the case where a doctor will ask for dates, so an app that quietly rewrites a logged start to fit its prediction fails before anything else is scored. None of the six below do that, which is why they made the list.
Irregular period tracker comparison: 6 apps at a glance
Clue: the one that admits when predictions stop helping
Clue is the best period tracker for irregular periods for most people because it does something unusual: it lets you hide its predictions. Clue’s own team describes cycles that vary so widely in length that regular predictions are “no longer useful”, and built a setting to show or hide them so the calendar can show only what you logged.
With predictions on, Clue works from your tracked history, and its App Store listing is upfront that it needs a few cycles of data before its estimates settle. With them off, you get the cleanest logged-days-only view of any app here, which is the view a doctor actually wants.
Two things to weigh. The deeper analysis tools sit behind Clue Plus, and the app cannot tell you why a cycle changed, only that it did. For how Clue’s data choices compare with the rest of the market, see which period trackers keep your data private.
Flo: the biggest app, with predictions that stay on
Flo’s App Store listing says it tracks your period “regular or irregular”, and Flo’s own guidance for people with irregular cycles is to use the app to spot patterns and changes that are useful in a conversation with a doctor. That is the right framing, and the symptom logging is the broadest of the six.
What Flo does not offer is a way to hide predictions, so on a cycle that swings by two weeks the predicted dates keep appearing and keep being wrong. It is a fine irregular period tracker if you can ignore the coloured circles and read your own log. Our post on what Flo’s predictions get right and wrong goes through the accuracy question in detail, and the Flo alternatives guide covers the switch if you decide to leave.
Apple Health: the free one that notices patterns for you
If you have an iPhone, Cycle Tracking in the Health app is already installed and does one thing none of the paid apps here do for free. Apple’s support page explains that Cycle Deviation Detection can inform you if your logged history from the previous six months shows a pattern of irregular cycles, infrequent periods, prolonged periods or persistent spotting. You pick which deviations you want alerts for, and you can review and export the cycle history from the same screen.
Predictions still appear as red-striped circles, and Apple is clear that they are based on the periods and cycle lengths you logged, so the same calendar limitation applies. The difference is that Apple is watching the shape of six months of data, not just projecting the last cycle forward. For someone who wants a free record plus a nudge when the pattern drifts, this is the pick.
Spot On: the one with no predictions unless your cycle is regular
Spot On, from Planned Parenthood, takes the most conservative position of the six. Its product page says you receive period predictions if you have regular periods, and that fertile-window predictions are likewise available if your periods are regular. With an irregular cycle, the app logs what you enter and does not draw a circle it cannot justify.
It also tracks birth control methods including the pill, patch, ring, shot, IUD and implant, with reminders, which matters because hormonal methods are a common reason cycles look irregular in the first place. The trade-off is that the app is deliberately plain: no deep insights, no export polish, no partner features.
Euki: the plain record you control
Euki is here for one reason. Its App Store listing describes an app that keeps your logs on your phone with no account, which makes it the simplest way to hold an honest, private record of an unpredictable cycle. Log the start, log the end, add symptoms, and nothing leaves the device unless you choose to share it.
It is not a prediction engine, and for an irregular cycle that is close to a feature. If your main worry is a clear history and privacy rather than forecasting, Euki does the job and asks nothing in return.
Otty: the one built so a partner can follow an unpredictable cycle too
Otty starts from the cycle length you set, anywhere from 20 to 60 days, and resets the count the day you log a period start. That means a short cycle or a long one simply becomes the record: the past cycle keeps its real length in your cycle history, where you can also move a start or end date if you logged it late.
The part that matters for irregular cycles is what Otty does when a period is overdue. Instead of silently rolling into a new cycle, the calendar marks those days as estimated and says so in plain words: no period start has been logged since a given date, so these days are estimated from your usual cycle, and logging the next start replaces the estimate. Otty never averages your history or claims to learn your cycle. It shows you the guess as a guess.
Otty is also the only app here with a proper partner view. The person you share with sees the same phase timeline and daily tips written for them, so an irregular cycle stops being a surprise for two people instead of one. Sharing is opt-in and item by item, as described on the share-your-cycle page, and cycle data stays on the device by default with sign-in optional. If a partner is part of the reason you are choosing an app, the full comparison lives in the best period tracker for couples guide.
Otty is iOS only, with a free 7-day trial and then a subscription, so it is the wrong pick for an Android household or for anyone who wants a free forever app.
How to track irregular periods, whatever app you use
How to track irregular periods comes down to logging the same two facts every cycle and refusing to let the app’s guess overwrite them. The routine below works in all six apps.
When are irregular periods worth a doctor visit?
Irregular periods are worth a doctor visit when the pattern is new, the gaps fall outside the normal range, or bleeding is unusually heavy. Most of the time they are not a sign of a problem, and the tracker’s job is to give you the dates that make the conversation quick.
What is normal. The NHS counts periods as irregular when the gap between them is less than 21 days or more than 35 days, and notes they are more likely to be irregular when periods first start in puberty and when you are nearing menopause. Cleveland Clinic adds that menstrual irregularities are fairly common and you do not have to predict your cycle to the exact day for it to count as normal. Our pillar on what counts as an irregular period goes through the definitions in full.
When it is worth a check. The Office on Women’s Health lists these as reasons to call a doctor:
– You get irregular periods after having had regular cycles.
– Your period comes more often than every 24 days or less often than every 38 days.
– Your cycle length varies by more than 20 days from month to month.
Cleveland Clinic adds missing three or more periods in a row, and soaking through one or more pads or tampons in an hour. If a late period is the specific worry, why your period is late covers the common causes besides pregnancy.
What to do. Book the appointment and bring the logged history from whichever app you use. The NHS advice is simply to speak to a GP if your periods are irregular or your normal pattern changes, and six months of start and end dates is the most useful thing you can hand over.
