Period Calculator
Next Period Starts
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Next Fertile Window
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Next 6 Predicted Periods
| # | Period Start | Period End | Fertile Window |
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How the Period Calculator Works
This period calculator predicts your upcoming menstrual periods by using the start date of your last period and your average cycle length. It projects the next six cycles, showing period start and end dates along with the estimated fertile window for each cycle, helping you plan ahead with confidence.
The calculation is straightforward: each new period is predicted to start one cycle length after the previous one. Your period end date is calculated by adding your period duration (typically 3-7 days) to the start date. The fertile window for each cycle is estimated using the same method as ovulation calculators: ovulation occurs approximately 14 days before the next period, and the fertile window spans from 5 days before ovulation through 1 day after.
Tracking your period over several months helps you identify your personal pattern and average cycle length. While the average cycle is 28 days, normal cycles can range from 21 to 35 days. Factors such as stress, travel, weight changes, exercise habits, and hormonal fluctuations can all affect your cycle timing. For the most accurate predictions, update this calculator regularly with your actual period start dates. If you notice significant irregularities or changes in your cycle, consider consulting a healthcare provider to rule out any underlying conditions.