How do ovulation calculators work out your most fertile period?

Fertility calculators help to estimate the day of ovulation and, therefore, the days when you are most likely to get pregnant. However, these types of tools are more accurate when the menstrual cycle is regular.These calculators should not be used as a method of contraception.
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Ovulation Calculator::Appstore for Android

When in the month are women and men most fertile? » British Fertility Society

Check Ovulation Calculator & Calendar

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How To Use An Ovulation Calculator - The Fertility Foundation

When Do I Ovulate?

Ovulation Calculator — Find Out When You Are Most Fertile

Ovulation Calculator : Estimate your most fertile days - Clearblue