Menstrual Cycle Calculator
Calculate your next period, ovulation date, and fertile window based on your cycle
Last Period Start Date
About Menstrual Cycle Calculator
This calculator predicts your next period, ovulation date, and fertile window based on your cycle length and last period date. Ovulation typically occurs 14 days before the next period starts. The fertile window is the 5 days before ovulation plus the ovulation day itself. Predictions are based on average cycle patterns and are meant as a guide — actual dates may vary.
FAQ
- What is a normal menstrual cycle length?
- A normal menstrual cycle is typically 21 to 35 days, with the average being 28 days. Cycle length is counted from the first day of one period to the first day of the next. Cycles shorter than 21 days or longer than 35 days may warrant a discussion with a healthcare provider.
- When do I ovulate?
- Ovulation typically occurs about 14 days before your next period. For a 28-day cycle, this is around day 14. For a 30-day cycle, it would be around day 16. However, ovulation timing can vary and is not always predictable with simple calendar methods.
- What is the fertile window?
- The fertile window is the period when conception is possible. It includes the 5 days before ovulation (since sperm can survive up to 5 days) plus the day of ovulation itself. That's a 6-day window each cycle when pregnancy is most likely to occur.
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