Ovulation Calculator

Estimate the likely ovulation day and fertile window from cycle dates and usual cycle length.

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Input

Enter the first day of the last period, your usual cycle length, and period length to estimate likely ovulation timing. This tool shows the result instantly without step-by-step output.

Input summary

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How to use Ovulation Calculator

Add your recent cycle dates, and the calculator will estimate when ovulation and the highest-fertility window are most likely to occur.

What this calculator is for

This calculator is for cycle awareness and fertility planning. It helps turn menstrual timing into an ovulation estimate, while recognizing that real ovulation can shift from cycle to cycle.

Tips

The result is more reliable when your cycle length is fairly regular from month to month.
Ovulation estimates are not a guarantee of fertility or a guarantee against pregnancy.
If cycles are highly irregular, ovulation testing or clinical guidance may be more useful than date prediction alone.