periods.day
Private cycle tracker
Tap a calendar date to get started
Track and share your cycle with the people you choose. Not advertisers.
Tap every day of your most recent period. Add an earlier period to make the estimate more personal.
Period days logged
0 days
Estimated cycle length
28 days
Typical period length
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Tap every day you bled to add or remove it
01
Tap every day you bled. Add earlier periods for a more personal estimate.
02
See your estimated phase, fertile window, and next period, then share the link with someone you trust.
03
Bookmark or keep the link to return and add new days later. periods.day does not save it for you.
periods.day has no accounts, cookies, analytics, or saved cycle data. Your entries live only in the link.
Anyone with the full link can see your entries. Share the link only with people you trust.
I was tired of having something as simple as tracking my cycle used to target me with ads for period underwear, fast food, or makeup. I wanted to understand my body and what it needs without advertisers exploiting that information. That’s why I built this site.
periods.day uses the period days you enter to estimate where you may be in your cycle. The more past periods you add, the more personal the estimate becomes. It’s still only an estimate.
Your dates and tracking goal are encoded in the URL after # and read in your browser. That fragment is not sent with the page request. periods.day does not use accounts, cookies, analytics, or browser storage. Anyone with the full link can read the data.
Don't be silly. Calendar predictions cannot identify safe days and should not replace contraception. Cycle timing can change, and pregnancy can occur outside a predicted fertile window. Read ACOG fertility guidance
It is an estimate of the days when pregnancy is more likely. ACOG describes the fertile period as roughly the five days before ovulation through one day after; ovulation itself can shift from cycle to cycle.
Predictions are less reliable when cycle length varies. Log every day of several periods for more personal estimates, and talk to a clinician if you are worried about your cycle.
The full URL includes the dates and tracking goal you entered. Anyone you share it with sees the same estimate and can change it in their own browser. Treat the link as private: the data is encoded, not encrypted.