Period and Ovulation Calendar
When your next period is due, your likely fertile days and whether you are late. Private: everything stays on this device.
Get started
Not sure about the numbers? Leave them as they are. After you log your next period the app uses your own cycles instead.
Estimates from your past cycles. Not medical advice and not birth control.
- Period
- Expected period
- Fertile
- Ovulation
- Notes
How did you feel? (optional)
Your periods
Calendar, sharing and settings
Settings
What you log is saved only in this browser on this device. Your data is never sent anywhere. Save a backup file now and then, or to move to another phone or computer.
This browser is not saving your data (private mode or storage blocked). It stays only until you close this page. Use Save backup file to keep it.
Questions
How is my next period worked out?
A cycle is the days from the first day of one period to the first day of the next. The app takes the average of your last six cycles and adds it to the day your last period started. With cycles of 28, 29, 27, 30 and 29 days the average is 29, so a period that started on 1 October is next expected on 30 October. Your shortest and longest cycles give the usual range: 28 to 31 October.
How is the fertile window worked out?
The egg is usually released (ovulation) about 14 days before the next period. Sperm can live up to 5 days, so the fertile window is the 5 days before ovulation, ovulation day and the day after. If your cycles vary, the window is widened to cover your shortest and longest cycle. Clear, stretchy discharge is a sign you are near ovulation; you can tick it on the day.
Can I use this as birth control?
No. Calendar estimates are not reliable enough to prevent pregnancy, because ovulation can come early or late in any cycle. Use contraception and talk to a doctor or nurse about what suits you.
My period is late. What now?
A few days late is common, especially with stress, illness, travel or a change in weight. If you could be pregnant, a home pregnancy test is reliable from the day your period was due. If you are not pregnant and periods are often more than a week late, or cycles are shorter than 21 or longer than 35 days, mention it to a doctor.
I missed logging a period, or I was pregnant. Will it spoil my average?
Add the missed period with Add a period you forgot to log. If you cannot remember it, tick Don't count the gap before this period on the period after the gap. Gaps of 90 days or more are left out by themselves. While pregnant or breastfeeding, tick pause predictions in Settings.
Is it private?
Yes. No account and no sign-up. What you log stays in this browser on this device and is never sent anywhere. The app works offline once it has loaded. Use Save backup file to keep a copy or move to another device.