Period Calculator
Track and predict menstrual cycle dates.
How to Do It Manually
Period timing is based on your cycle length. Multiply the number of cycles by your average cycle length to predict future period dates.
Next Period ≈ First Day of Last Period + (Cycle Length in days)
- Track the first day of your periods for 2–3 cycles.
- Calculate average cycle length (days from one period to the next).
- Add the cycle length to the last period's start date.
Frequently Asked Questions
Is my cycle length normal?
Average is 21–35 days. Anything within that range is normal; variation is common.
Why is my cycle irregular?
Stress, exercise, diet changes, hormonal contraceptives, and medical conditions all affect cycles.