Period & Ovulation Tracker
a private cycle calendar that predicts your period, fertile window and ovulation
Tap the days your period started and this tracker fills in your predicted periods, fertile window, and estimated ovulation — all on one calendar. No account, no cloud, no subscription: your cycle data is saved only in this browser and never leaves your device.
Track your period and ovulation — privately
This is a free period and ovulation tracker that lives entirely in your browser. You tap the days of each period — including when it ends — and it predicts your upcoming periods, draws your fertile window, and marks your estimated ovulation day on a single calendar. There is no account, no email, no subscription, and no cloud — every date you enter is saved only on this device, so your reproductive data never leaves your hands. If you have been looking for a private, no-account period tracker online and free, this is built for exactly that.
It works for two everyday goals. If you are trying to conceive, the highlighted fertile window shows the days you are most likely to get pregnant. If you are tracking to understand your body — or simply want to know when your next period is due — the calendar and the Today panel keep it one glance away. The same simple period and ovulation tracker serves both without ever asking who you are.
How it works
- Mark your last period. Tap each day of your most recent period on the calendar; the first day starts your cycle. Even a single day is enough to begin predicting.
- Add a few past periods. Mark the days of one or two earlier periods. With two or more logged, the tracker learns your average cycle and period length automatically.
- Read your predictions. The calendar fills in your predicted upcoming periods, your fertile window, and your estimated ovulation day, each colour-coded with a legend.
- Check the Today panel. See your current cycle day, the phase you are in, how many days until your next period, and your next fertile window at a glance.
- Keep it private. Everything is saved only in this browser. Export a JSON or CSV backup whenever you want, or erase every entry with one button.
How the calendar method predicts your cycle
A menstrual cycle is counted from the first day of one period to the first day of the next. This period and ovulation calculator looks at the gaps between the first days of the periods you have logged and averages them into your typical cycle length; with a single period logged, or in Manual mode, it uses the cycle length you set. Adding that average to your most recent start date gives your next predicted period, and repeating it fills in the months ahead.
Ovulation tends to happen about 14 days before the next period begins, because the luteal phase is relatively constant even when cycle length varies. So your estimated ovulation day is placed 14 days before each predicted period, and your fertile window is drawn as the six days up to and including that day — the span when conception is most likely. These are statistical estimates from your dates, not a measurement of your body, which is why even the most accurate period and ovulation tracker built on the calendar method is a guide rather than a guarantee.
Private by design — your data never leaves your device
Many popular period apps store your cycle, symptoms, and fertile days on their servers behind an account. This one does the opposite: it is 100% client-side. Nothing is uploaded, there is no login, and there are no analytics watching what you log. Your entries are written to your browser's local storage and stay there. That is the whole point — a free period and ovulation tracker with no subscription that you can use without handing your reproductive data to anyone. You can export a JSON or CSV copy for your own backup at any time, and the delete button wipes every entry from this browser in a single tap. Because the data is local, clearing your browser data or using private browsing will reset it, so keep an export if you want to move devices.
Frequently asked questions
Does my period and ovulation data leave my device?
No. This period and ovulation tracker is 100% client-side: every date you log is saved only in your own browser's local storage. There is no account, no server, no cloud sync, and nothing about your cycle is ever uploaded or shared. Your data never leaves your device.
Do I need an account or a subscription?
No. There is no sign-up, no email, no subscription, and no cost. Open the page and start logging — the free period and ovulation tracker works immediately and remembers your data on this device.
How are my fertile window and ovulation day calculated?
It uses the calendar method. Your estimated ovulation day is placed about 14 days before your next predicted period, and your fertile window is the six days up to and including that estimated ovulation day. These are statistical estimates, not a measurement of your actual ovulation.
How does it predict my next period?
It averages the lengths of the cycles you have logged and adds that to your most recent period start date. With only one period logged, or in manual mode, it uses the cycle length you set. The average is kept within a sensible 20-to-40-day range.
Can I record how long my period lasts?
Yes. Tap every day of your period on the calendar, not just the first — the run of marked days is your period, so its length is recorded too. The tracker shows your average period length and uses it to draw future periods. Stop marking when your period ends, and tap any day again to remove it.
Can I use this to avoid pregnancy?
Not on its own. Calendar-based predictions are estimates and cycles vary, so this tool is not a reliable form of contraception by itself. If you are avoiding pregnancy, use it only alongside a method recommended by a healthcare professional.
Can I use it to plan to get pregnant?
Yes, as a guide. The highlighted fertile window shows the days you are most likely to conceive, which many people find helpful when trying to conceive. For more precision, pair it with ovulation tests and speak with a healthcare professional.
Is this the most accurate period and ovulation tracker?
It is as accurate as the calendar method allows, which depends on how regular your cycles are and how many you have logged. Regular cycles with several logged months predict well; irregular cycles are harder for any calendar-based tracker. It is not a substitute for medical-grade ovulation testing.
Can I export or delete my data?
Yes. Export your period start dates and settings to a JSON or CSV file at any time for backup, and use the delete button to erase every entry from this browser in one tap. You are always in full control of your data.
Does it work offline?
Yes. Once the page has loaded, the calendar, predictions, and export all run entirely in your browser with no connection. Because your data lives in local storage on this device, clearing your browser data or using private browsing will reset it — export a backup if you want to keep it.