Period Calculator

Estimate the next period date and other common cycle milestones from recent menstrual timing.

Preparing Period Calculator

Please wait ...

Input

Enter the first day of the last period, the usual cycle length, and the usual period length to estimate the next cycle dates. This tool shows the result instantly without step-by-step output.

Input summary

Your calculator summary shows here.

How to use Period Calculator

Add your recent period timing, and the calculator will project the next expected cycle dates from that pattern.

What this calculator is for

This calculator is for cycle tracking, planning, and period prediction when you want a simple date-based estimate of what comes next in the cycle.

Tips

Predictions are most useful when cycles are fairly consistent over time.
Stress, illness, travel, weight change, and other factors can shift a cycle even when past cycles looked regular.
If bleeding patterns change sharply or become hard to predict, a clinician can help decide whether that pattern needs evaluation.