Fertile Window Calculator
Pregnancy is only possible on about 6 days per cycle — the five days before ovulation plus ovulation day itself. Find your 6 days for this cycle and the next three.
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Peak day (ovulation)
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Your 40-week timeline
Heartbeat ~8w
Anatomy scan ~20w
Full term 39w
You
1st trimester2nd trimester3rd trimester
Week 1Week 13Week 27Due · 40
Based on Naegele's rule (ACOG methodology). Estimates only — always confirm with your provider.
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Why the fertile window is 6 days
An egg survives only about 24 hours after ovulation, but sperm can live up to 5 days inside the reproductive tract. Put together, that means intercourse anywhere from 5 days before ovulation through the day after can lead to pregnancy — a 6-day window. The highest-probability days are the two days right before ovulation, when sperm are in place and waiting as the egg is released.