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Tracking cycle length makes it possible to predict upcoming period dates well in advance, which is useful for planning and for noticing irregular cycles.
This calculator projects your next two expected period start and end dates from your last period date, typical cycle length, and typical period length.
How it works
Enter the start date of your last period, your typical cycle length in days, and your typical period length in days. The calculator adds the cycle length to the last period date to project the next period, and repeats for the one after that.
- Enter first day of your last period.
- Enter average cycle length (days).
- Enter average period length (days).
- Click Calculate to see your results.
Examples
Last period July 1, 28-day cycle
With a last period starting July 1 and a 28-day cycle, the next period is projected to start July 29 and end August 2, with the following period starting around August 26.
Who should use it
- General planning around expected period dates.
- Noticing when actual cycles start deviating significantly from the typical pattern.
Industry applications
- Personal health tracking
- Wellness and lifestyle apps
Advantages
- Projects two cycles ahead in a single calculation.
- Works with any typical cycle and period length, not just a fixed 28-day assumption.
Limitations
- Predictions are less reliable for those with irregular cycles.
Common mistakes to avoid
- Using an outdated or inaccurate cycle length that doesn't reflect recent, actual cycle patterns.
- Treating the projected dates as guaranteed rather than an estimate based on typical timing.
Best practices
- Update your cycle length figure periodically based on your most recent few cycles for the most accurate predictions.
Tips
- If your actual period consistently starts several days earlier or later than predicted, update your typical cycle length figure to improve future predictions.