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Free calculatorFertile Window Calculator
Find your fertile window — the 6 days each cycle when you can conceive — and the best days to try, from your last period and cycle length.
Frequently asked questions
What is the fertile window?
The fertile window is the roughly 6 days ending on ovulation day — the 5 days before ovulation plus ovulation itself — because sperm can survive up to 5 days.
Which are the best days to conceive?
The 2-3 days just before ovulation and ovulation day are the most fertile. Having sex every 1-2 days across the window gives the best chance.
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Note: These calculators give estimates for general guidance only and are not a substitute for medical advice. Your doctor confirms your dates and due date by ultrasound.