Period Calculator

Predict your next period, fertile window, and upcoming cycle dates.

Enter Your Values

First Day of Last Period

Average Cycle Length (days)

Average Period Duration (days)

Results

Fill in your values above and click Calculate.

Frequently Asked Questions

Q.How regular are menstrual cycles?

Normal cycles range from 21-35 days. Variations of a few days each month are common. Track 3+ cycles for a more accurate average.

Q.What factors affect cycle regularity?

Stress, illness, weight changes, travel, and hormonal conditions can all affect cycle timing. Significant irregularity warrants a doctor visit.