About this tool
A period calculator (menstrual cycle calculator, next period date calculator) estimates when your next period may start by counting forward from the first day of your last one.
The cycle length is the number of days from the first day of one period to the first day of the next; many people have cycles around 21 to 35 days, and 28 is only a common example.
Next date = last start date + cycle length. For example, if your last period began on 1 March and your cycle is 28 days, the next one is expected on 29 March, and the following one on 26 April.
The tool also shows how many days are left and about when the period ends, using the period length you enter. When will my next period come?
The answer is an estimate, because stress, travel, sleep, illness and other things can shift a cycle by days. Is a late date a sign of something? This tool cannot say.
Months and days are listed separately so the year never gets in the way. To see fertile days and an ovulation estimate, use the ovulation calculator instead.
Your dates are calculated in your browser and are not saved or sent anywhere.
ⓘ It is not a medical test, not a diagnosis and not a method of contraception, so talk to a doctor about long delays, very irregular cycles or pain.
How to use
- Pick the first day of your last period.
- Enter your usual cycle length in days and how many days your period lasts.
- Read the days left and the next three expected start dates.
- Treat the dates as estimates and see a doctor about long delays or pain.