Period & Fertility Calculator

How Our Calculator Works

Our calculator uses scientifically-backed algorithms to provide accurate predictions for your menstrual cycle, ovulation, and fertility window.

Period Prediction

We calculate your next period by adding your average cycle length to the first day of your last period. For example, if your cycle is 28 days long and your last period started on April 1, your next period would be expected around April 29.

Ovulation Calculation

Ovulation typically occurs 14 days before the start of your next period. Our calculator determines this date based on your cycle length. Understanding your ovulation day is crucial for both conception planning and contraception.

Fertility Window

Your fertility window includes about 5 days before ovulation and the day of ovulation itself. This is when pregnancy is most likely to occur if you have unprotected sex. Sperm can survive in the female reproductive tract for up to 5 days, while an egg is viable for about 24 hours after ovulation.

Pregnancy Due Date

If you're pregnant or planning to conceive, we calculate your estimated due date based on the first day of your last period. This follows the standard medical calculation of adding 280 days (40 weeks) to the start of your last period.