Predict upcoming period start dates from the first day of your last period and your usual cycle length.
Cycle timing can vary naturally. This is a calendar estimate only and should not be used to diagnose pregnancy, fertility, abnormal bleeding or a menstrual disorder.
Maintained by Live Fitness Check. Last updated: August 13, 2026. How we test our calculators .
The calculator adds your usual cycle length to the first day of the last period and advances by the same interval until it reaches the next predicted future start.
It may be less useful when cycle length changes significantly from month to month because the calculation assumes the cycle length entered repeats.
No. This page is intentionally focused on predicted period dates; fertility calculations are handled by separate ovulation tools.
