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Ovulation Calculator

Find your fertile window and estimated ovulation day to plan (or avoid) pregnancy.

Your cycle

Leave the luteal phase at 14 days unless a doctor has told you otherwise — it's the most common length and varies little between women.

Your results

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Estimated ovulation day
💚 Most fertile window—
🎯 Peak fertility days—
🩸 Next period expected—
🤰 If you conceive, due date—

These are estimates based on averages. Cycles vary month to month — ovulation predictor kits and tracking give the most reliable picture.

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When are you most fertile?

Your fertile window is the roughly 6 days ending on ovulation day — the 5 days before, plus ovulation itself. Sperm can survive up to 5 days, while an egg lives about 24 hours, so the days leading up to ovulation are the most fertile.

How ovulation is estimated

Ovulation typically happens about 14 days before your next period (the luteal phase), not 14 days after your last one. So: ovulation day = last period date + cycle length − luteal phase. That's why cycle length matters so much.

Is the fertile window the same every month?

No. If your cycle length varies, so does ovulation. Track a few cycles for a better average, and consider ovulation tests for precision.

Can I use this to avoid pregnancy?

Calendar estimates alone are not a reliable form of contraception. Use a proper method if you're avoiding pregnancy.