🌸 Period Calculator
Predict your next periods, fertile window and ovulation date.
🥚 FERTILE WINDOW & OVULATION
Enter your last period date to see predictions.
This period calculator predicts your next 6 menstrual periods based on your cycle length and last period date. It also calculates your fertile window and estimated ovulation date. Results are estimates — actual timing varies from cycle to cycle.
Frequently Asked Questions
How long is a normal menstrual cycle?
A typical cycle is 21–35 days, with 28 days being average. The length is counted from the first day of one period to the first day of the next. Cycles can vary month to month by several days even in healthy individuals.
When is the fertile window?
The fertile window is the 5 days before ovulation plus the day of ovulation — about 6 days total. Sperm can survive up to 5 days inside the reproductive tract, so intercourse in the days leading up to ovulation can result in pregnancy.
When does ovulation typically occur?
Ovulation typically occurs 14 days before your next period (the luteal phase). In a 28-day cycle that's day 14. In a 32-day cycle that's around day 18. This calculator uses your luteal phase length to estimate ovulation.
Is this a reliable form of birth control?
No. Calendar-based methods have high failure rates. For reliable contraception, consult a healthcare provider.