Estimate the next period start and following cycle from the first day of a recent period and your typical cycle length. Enter the usual number of bleeding days to see an approximate end date for the current period. The tool accepts adult cycle lengths from 21 to 45 days and recent period dates; real cycles can vary from month to month. Calendar forecasts cannot diagnose a condition, rule out pregnancy or provide reliable contraception.
Enter the first day of a recent period.
Set your typical cycle length and period length in days.
Review the estimated next start, current-period end and following cycle date.
Next period estimate: Last period start + average cycle length
Estimated period end: Last period start + period length − 1 day
Can this predict exactly when my period will start?
No. It extrapolates the average cycle length you enter. Cycles can shift, so treat dates as estimates.
Can I use this as birth control?
No. Calendar predictions are not reliable contraception. Seek qualified health advice about contraceptive options.