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Ovulation Calculator

Find your ovulation date and most fertile days. Enter your last period date and cycle length for instant results.

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About This Tool

What it does

Calculates your estimated ovulation date, fertile window and next period date based on your last period and average cycle length. Also shows the ovulation dates for the next 3 cycles so you can plan ahead.

Who it's for

Women trying to conceive or understand their cycle. Most useful for those with regular cycles. Used in the UK, US, Australia, Canada, India, Singapore and worldwide.

Your privacy

All calculations happen in your browser. No data is transmitted or stored anywhere.

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⚠️ For informational purposes only. This tool provides estimates and is not a reliable method of contraception. Always consult a healthcare professional for fertility advice. Sources: NHS, ACOG.

Frequently Asked Questions

How is my ovulation date calculated?
Ovulation typically occurs 14 days before your next period. The calculator adds (cycle length minus 14) days to your last period date. For a 28-day cycle that is day 14. For a 32-day cycle it is day 18.
What is the fertile window?
The fertile window spans the 5 days before ovulation and ovulation day itself — 6 days total. Sperm can survive up to 5 days in the reproductive tract which is why the days before ovulation are included.
How accurate is an ovulation calculator?
Most accurate for women with regular cycles. Stress, illness and hormonal factors can shift timing. For fertility treatment or medical decisions always consult a healthcare professional.
What are signs of ovulation?
Common signs include changes in cervical mucus (clearer and more slippery), a slight rise in basal body temperature, mild pelvic discomfort and a positive ovulation predictor kit (OPK) result.
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