periods.day
Online period day calculator
Add your latest period days
Log recent period days to estimate your next period, cycle length and upcoming dates. Your entries stay in your private link.
Mark each bleeding day from your most recent period. Adding earlier periods can make the estimate more personal.
Period days logged
0 days
Estimated cycle length
28 days
Typical period length
—
Log every day you bled. Hover or hold a date to explore the estimate for that day.
01
Mark every day you bled during your latest period. Add earlier periods when you know them to personalize the cycle estimate.
02
Use the current-cycle summary for today, then browse any month and hover or hold a date for its estimated phase.
03
Predicted dates can move. Save your private link to update the calculator when your next period begins.
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.
It uses the bleeding days you log to estimate a cycle length and upcoming period dates. With little history, it starts from a 28-day baseline; more complete period history can personalize the estimate.
No. Period dates are estimates. Stress, illness, travel, medication and normal variation can change when bleeding begins.
Enter the days you actually bled, not the date you expect a period or the date you had sex. Future highlighted dates are predictions and do not become entries when you inspect them.
No. A period-date calculator cannot identify safe days, confirm ovulation or replace contraception. Use a reliable contraceptive method if avoiding pregnancy matters to you.