Health calculator
Ovulation Calculator
Estimate ovulation and fertile window dates from cycle length and last period date.
Formula
Ovulation estimate
Cycle estimates are not contraception, diagnosis, or fertility treatment advice. Consult a qualified clinician for medical guidance.
Ovulation date = next period date - 14 days
For a 28-day cycle, ovulation is estimated around day 14.
FAQs
Is ovulation always 14 days before the next period?+
No. It is a common estimate and can vary by person and cycle.
How does the Ovulation Calculator calculate the result?+
It uses the Ovulation estimate: Ovulation date = next period date - 14 days. For a 28-day cycle, ovulation is estimated around day 14.
What information do I need to use the Ovulation Calculator?+
Estimate ovulation and fertile window dates from cycle length and last period date.
How accurate is the Ovulation Calculator?+
Ovulation Calculator applies the formula and assumptions shown on this page. Results may be rounded for readability, so verify changing rates, thresholds, medical guidance, or legal rules with the cited source or a qualified professional.
What should I check before using the Ovulation Calculator result?+
Check that the units, dates, rates, and assumptions match your situation. Change one input at a time to understand which values have the largest effect on the result.
Health guide
How to use the Ovulation Calculator
Estimate ovulation and fertile window dates from cycle length and last period date. The page also explains the ovulation estimate and shows a practical example: For a 28-day cycle, ovulation is estimated around day 14.
- 1
Enter your details
Enter cycle length and last period date, then complete any other fields shown in the calculator.
- 2
Check the calculation
Review the result alongside the ovulation estimate: Ovulation date = next period date - 14 days.
- 3
Compare scenarios
Change one or more inputs to see how they affect the ovulation Calculator result before you use the estimate.
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