Ovulation Calculator
HealthPredicts the likely days of ovulation based on the first day of your last menstrual period and the length of your typical menstrual cycle. This calculator provides an estimate and should not be used as a method of birth control.
How to use this calculator
Start with your values, or try a preset.
Enter First Day of Last Menstrual Period and Typical Cycle Length (days) in the units shown.
Read Estimated Ovulation Day, Estimated Fertile Window Start, and Estimated Fertile Window End in the results panel. Results update as you change the inputs.
Choose a preset to load an example, then adjust the values for your situation.
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Use the result as an estimate and confirm any medical decisions with a qualified professional.