What’s a normal cycle?
The limits used by the International Federation of Gynecology and Obstetrics (FIGO) for adult women.
| Normal | See a doctor if | |
|---|---|---|
| Cycle length | 24 to 38 days | shorter than 24 or longer than 38 days |
| Period length | Up to 8 days | longer than 8 days |
| Regularity | Shortest and longest cycle within 7–9 days | the difference is larger |
| Missed periods | no period for 3 months or more, without pregnancy |
FAQ
How do I work out my cycle length?
Count the days from the first day of one period to the first day of the next. If you don’t know it, add your past period dates and we’ll average them.
My period is late. What should I do?
If you might be pregnant, take a home pregnancy test. If it keeps happening or your period stops for 3 months, see your doctor.
Why does my cycle change from month to month?
A few days’ difference is normal and can come from stress, travel, weight change or breastfeeding. The calculator tells you if the difference is large.
Can I use this for birth control?
No. Ovulation can shift in any cycle, so don’t rely on it to avoid pregnancy.
Do you store the dates I enter?
No. Everything is calculated in your browser; no date is sent anywhere.