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Ovulation Calculator

Calculate ovulation day and fertile window

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📖 How to Use

Enter the first day of your last period
Click Calculate to see ovulation day and fertile window

📐 Formula

Ovulation day ≈ day 14 of cycle (for a 28-day cycle)
Fertile window = 5 days before to 1 day after ovulation
Next period = last period + cycle length

❓ FAQ

What if my cycle is irregular?▾

Ovulation estimates are less reliable with irregular cycles. Consider using ovulation tests or basal body temperature tracking.

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About Ovulation Calculator

This tool is completely free, no registration required. Works directly in your browser. Supports both PC and mobile devices.

Ovulation Calculator is a free online tool that works on both PC and mobile. No registration or download required — just open in your browser. Results are accurate and reliable for everyday use and professional reference.