Ovulation & Fertility Calculator

Estimate your fertile window, ovulation day, next period and useful cycle dates with a responsive, ad-heavy calculator page.

Calculate Your Fertile Window

Enter the first day of your last period, your average cycle length and luteal phase to estimate your most fertile days and next period date.

First Day of Last Period Average Cycle Length (Days) Period Length (Days) Luteal Phase Length (Days) Display Future Cycles Date Format Region

Period

Fertile Window

Luteal Phase

Estimated Ovulation Date —

Fertile Window —

Best Days To Try —

Next Period —

Period Ends—

Fertile Window Starts—

Fertile Window Ends—

Implantation Estimate—

Earliest Test Date—

Next Cycle Ovulation—

Your ovulation and fertility estimate will appear here.

What Is an Ovulation Calculator?

An ovulation calculator estimates when ovulation may happen during your menstrual cycle. It can also estimate your fertile window, which is the group of days when pregnancy is more likely.

How To Use This Fertility Calculator

Enter the first day of your last period, your average cycle length and your luteal phase length. The calculator estimates ovulation by counting back from your next expected period. These dates are estimates only and cycles can vary.