Ovulation Calculator
Estimate ovulation and a possible fertile window from cycle dates.
Estimated fertile window: July 29, 2026 to August 4, 2026.
If conception occurs near this estimate, the due date is approximately April 26, 2027.
How to use this calculator
- Enter the latest period start and average cycle length.
- Review the live result and use Copy result when you need to share it.
How the calculation works
Ovulation is approximated as cycle length minus 14 days after the period start; the displayed window spans five days before through one day after.
Formula
Ovulation is approximated as cycle length minus 14 days after the period start; the displayed window spans five days before through one day after.
Step-by-step calculation
- Enter the latest period start and average cycle length.
- Ovulation is approximated as cycle length minus 14 days after the period start; the displayed window spans five days before through one day after.
- Check the displayed result, then copy it if needed.
Worked example
For a 28-day cycle, estimated ovulation is near cycle day 14.
Risk guidance
Frequently asked questions
Does this tool send my inputs anywhere?
No. The interactive calculation runs in your browser and this site does not submit tool inputs to a backend.
How should I use the result?
Check that the entered units and values match your situation, especially around dates, breaks, and rounding.
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