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Predict ovulation, fertile window, and next period with a 6-month forecast.
Estimate your most fertile days from your last menstrual period, average cycle length, and luteal phase length. See your predicted ovulation day, 6-day fertile window, implantation window, next period date, a color-coded view of your current cycle, and a 6-month forward forecast. Everything is calculated instantly in your browser — nothing is uploaded or stored.
The Ovulation Calculator provides an instant, private estimation of fertile windows, ovulation days, and menstrual cycles directly in your browser. Because all calculations happen client-side without storing or uploading data, it ensures complete privacy. Users benefit from a 6-month forward forecast, implantation windows, and a color-coded cycle view entirely for free without requiring a software installation or account setup.
Good to know: This tool provides estimates based on mathematical averages and standard cycle parameters, so it should not replace professional medical advice, clinical fertility tracking, or personalized medical diagnostics.
Follow these steps to predict your fertile window, ovulation day, and future menstrual cycles using our private browser-based calculator.
Enter your last period start date
Select the first day of your most recent menstrual period from the date picker to establish your current cycle baseline.
Input your average cycle length
Provide the typical number of days between your periods, usually ranging from 21 to 35 days, for accurate forecasting.
Adjust your luteal phase length
Enter the number of days between ovulation and your next period if known, or leave the default setting for a standard estimate.
Review your fertile window results
Examine the color-coded calendar to see your predicted ovulation day, 6-day fertile window, and expected implantation dates.
Check the 6-month forward forecast
Scroll down to view predicted dates for your future cycles and peak fertility windows over the next half year.
Estimated time: PT1M
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