Health & Fitness · Free tool
Ovulation Window Calculator
Fertile window, likely ovulation day, and next period estimate from last period date and cycle length.
Updated April 2026
Estimated ovulation day
Thu, May 7
Fertile window
Sat, May 2 – Fri, May 8
Next period estimate
Thu, May 21
Not medical advice — consult a provider for family planning decisions.
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What it does
Find your fertile window, ovulation day, and next period estimate.
Runs entirely in your browser — no upload, no account, no watermark. For more tools in this category see the full tools index.
How to use it
- Enter last period date.
- Set cycle length.
- Read fertile window.
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