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Menstrual Cycle Calculator

Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can calculate the beginning of period or menstrual cycle dates for the next 12 calendar months.

Enter the first day of your last period:

Cycle Length:

By adding your average cycle length, you can calculate for future dates to make your own private period tracker. Use our date calculator to add dates quickly.

Android: Use this period calculator offline with our all-in-one calculator app.

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Period dates calculation

The average menstrual cycle is 28 days long. Cycles can range anywhere from 21 to 35 days in adults and from 21 to 45 days in young teens. To find your cycle length, count the days from first day of one period to the first day of the next period.

The length of a woman's menstrual cycle will typically vary, with some shorter cycles and some longer cycles. A woman who experiences variations of less than eight days between her longest cycles and shortest cycles is considered to have regular menstrual cycles.

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