Using the calculator
Enter First day of last period, Average cycle length, Typical period length. Project upcoming period dates, cycle phases and estimated fertile windows from your typical cycle pattern.
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Menstrual Cycle Calculator
Project upcoming period dates, cycle phases and estimated fertile windows from your typical cycle pattern.
Enter your measurements and health details
Use current, consistently measured values for the menstrual cycle calculation. Results update automatically and are intended for education and planning, not diagnosis.
days
days
Estimated next period—
Estimated period end—
Estimated ovulation—
Estimated fertile window—
Important: Health results are educational screening and planning estimates. They are not a diagnosis and are not a substitute for medical care.
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How to use this calculator
Reading the result
The result shows project upcoming period dates, cycle phases and estimated fertile windows from your typical cycle pattern.
Results are estimates based on the values entered. Review the Methodology and Calculator Disclaimer for important limitations.