Period calculator
When is my next period?
Your next three periods from your last one, your real cycle length from the dates you remember, and — when cycles are irregular — a window instead of a day that will be wrong.
Runs in your browser. Nothing you enter is sent anywhere — open your browser's network tab and check.
From the first day of one period to the first day of the next. Not sure? Use "Cycle length from dates".
How it is calculated
The same rule the app uses
Next period is your last period start plus your cycle length. If that date has already passed, the tool steps forward in whole cycles until it lands on or after today — the same rule PinkyBloom's prediction uses, so the web and the phone agree.
Cycle length is the number of days between consecutive period starts. Give the tool two or more dates and it sorts them, measures each gap, and reports the average, shortest and longest. What FIGO measures is the spread between your shortest and longest cycle over the previous six months — not the change from one cycle to the next — and its limit moves with age: 9 days from 18 to 25, 7 days from 26 to 41, 9 days from 42 to 45. This tool uses 7, the band most adults fall in, so it errs towards offering a window rather than a day. Adults typically run 24 to 38 days (FIGO); the app assumes 28 until it has learned yours.
For irregular cycles the honest answer is a window: shortest cycle to longest cycle, counted from the last period. Perimenopause is the common reason a window widens after 40, and PinkyBloom's perimenopause mode predicts exactly this kind of window rather than pretending to know the day.
Questions
Asked in your words
The same math, on your phone
A prediction that learns your cycle
PinkyBloom does this from the periods you log, on your phone — the cycle length becomes yours, the forecast moves with it, and across perimenopause the prediction widens into a window on its own. If you pair, your partner's PinkyBond app gets the forecast in plain words, never the log.
Free on iPhone and Android. No account, no email, no phone number. Your health data stays on your phone unless you turn on iCloud backup or partner sharing — and we can't read it either way.
