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Ovulation Calculator
Predict your most likely ovulation day and fertile window from the first day of your last period and your average cycle length, plus when your next period is expected.
Free · No sign-up · Updated August 2026
Estimated ovulation day
Sun, Oct 4
Fertile window
Tue, Sep 29 – Mon, Oct 5
Next period expected
Sun, Oct 18
⚕️ Estimates for planning only — not a contraceptive method.
🔒 This tool runs entirely in your browser. Your data is never uploaded.
Frequently asked questions
How does it estimate ovulation?＋
From your cycle length and last period, it estimates your ovulation day and the fertile window around it.
How reliable is it?＋
It's an estimate based on average cycles; actual ovulation shifts with cycle variation, stress and health.
Is this medical advice?＋
No — for family planning or fertility concerns, consult a healthcare professional.