Menstrual Cycle Calculator
First Day of Last Period
Cycle Length (days)
Period Length (days)
A period (menstrual cycle) calculator predicts future menstruation dates based on cycle length and period duration. The average cycle is 28 days, but cycles from 21 to 35 days are normal. Tracking helps identify irregularities and plan around key life events.
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Pro Tip
Cycle irregularity of a few days is normal. Consult a doctor if cycles are consistently shorter than 21 days, longer than 35 days, or if you experience very heavy bleeding.
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Did You Know?
The word "menstruation" comes from Latin "mensis" (month) and Greek "mene" (moon). Many ancient calendars were based on the lunar cycle (~29.5 days), close to the average menstrual cycle.
References
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