Menstrual Cycle Calculator
Predict your next period, ovulation date and fertile window from your last period and average cycle length. See your next three period dates and the current day of your cycle. Based on the standard luteal-phase method used by cycle trackers.
How to use
1
Enter the first day of your last period
Use the calendar picker to select the date.
2
Enter your average cycle length
Type the number of days between periods (most women: 21–35).
3
Enter period duration
Type how many days your period usually lasts.
4
Read your prediction
See your next period date, estimated ovulation and fertile window.
Features
Next period prediction
See when your next period is likely to start.
Ovulation estimate
Get an estimated ovulation date based on your cycle length.
Fertile window
See the days when conception is most likely.
Next 3 periods
See the predicted start dates for your next three periods.
Current cycle day
See which day of your current cycle you are on.
Common use cases
- Predict your next period date
- Identify your fertile window for family planning
- Track your cycle for health monitoring
- Plan around anticipated period dates