Ovulation Calculator

Detect Your Fertile Days Using This Free Ovulation Calculator

To use the ovulation calculator, indicate the first day of your last menstrual period and input the average length of your menstrual cycle. Then click "Calculate."

Be aware that ovulation calculators are not the most accurate way to determine when you're ovulating. They can, however, be helpful. (Read more about the accuracy of ovulation calculators, or scroll down to read more about how this ovulation calculator works.)

This ovulation calculator determines your day of ovulation by counting 14 days backwards from the day you'd expect your next period. Fourteen days is the average length of the luteal phase, the time between ovulation and your period. It can vary in different people, with anything between 10 and 16 days being normal.

If you know from BBT charting that your luteal phase is longer or shorter than 14 days, you can use that information to adjust the calculator's results. So, for example, if you know that your luteal phase is usually 12 days, you might want to assume ovulation and your fertile days will be two days later than the calculator predicts.

The ovulation calculator gives you a wide range of dates for your fertile days, which will also help account for variations in luteal phases. The best way to use an ovulation calculator is to see it as a rough estimate, and not as a for-certain determination of ovulation.

More about ovulation:

• Signs of Ovulation
• Ovulation Symptoms Quiz
• Are Ovulation Calculators Accurate?

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