This tool estimates your next period from the first day of your most recent period. It also shows the range when your next period may arrive early, on schedule, or later than usual.

It also estimates the ovulation date, the days when pregnancy is more likely, and the days when pregnancy may be less likely, to help you track your cycle.

Important: The result is an estimate, not a medical diagnosis, and should not be used as a substitute for contraception.

Which date should I enter?

Enter the first day your last period started, not the day it ended. A menstrual cycle is counted from the first day of one period to the first day of the next.

For example, if your period started on June 1 and your average cycle is 28 days, the next period may start around June 29.

Understanding the “safer period” correctly

The days when pregnancy may be less likely are sometimes called the “safe period,” but they are not 100% safe.

Ovulation can shift because of stress, sleep, weight, hormones, or irregular cycles, and sperm can remain in the body for several days.

Use this result only to understand your cycle and make an initial plan. It should not replace contraception.

What should I do if my period is late?

If your period is later than the estimated range and pregnancy is possible, consider taking a pregnancy test, especially when your period is about one week late.

If your period stops for several months, frequently becomes irregular, is unusually painful, involves heavy bleeding, or continues to change, speak to a healthcare professional to investigate the cause.