🌸 Ovulation Calculator

About this Ovulation Calculator

Ovulation usually happens about 14 days before the next period starts, whatever the total cycle length. This calculator works backwards from your cycle length to estimate the ovulation day, then marks the fertile window: the five days before ovulation plus the day after, when conception is most likely to occur.

How to use it

1. Enter the first day of your last period.
2. Enter your usual cycle length in days (28 is average).
3. Press Calculate Ovulation.
4. See the ovulation estimate, fertile window and next period date.

Example

Last period 1 Mar with a 28-day cycle: ovulation falls on 15 Mar, the fertile window is 10 Mar to 16 Mar, and the next period is due 29 Mar.

Frequently asked questions

What is the fertile window?

The days around ovulation when an egg can be fertilised: roughly five days before ovulation and one day after.

Can I rely on this to avoid pregnancy?

No. Cycle timing alone is not a reliable contraception method because ovulation can shift by several days.

What if my cycle is irregular?

Predictions are less reliable with irregular cycles. Tracking temperature or ovulation tests gives a clearer picture.

More Health