What is the fertile window?

Bottom lineThe fertile window is the roughly 6 days when sex can lead to pregnancy: the 5 days before ovulation plus ovulation day, because sperm survive up to 5 days and the egg lives 12 to 24 hours. Your most fertile days are the 2 to 3 before ovulation; find it by estimating from cycle length, watching for egg-white cervical mucus, using LH kits, or tracking basal body temperature.

The fertile window is the span of days in your cycle when sex can lead to pregnancy. It's about 6 days long: the 5 days before ovulation plus ovulation day itself.

Why it's 6 days

• Sperm survive up to 5 days in the reproductive tract
• An egg lives only 12 to 24 hours after ovulation

So sperm present in the days before ovulation can still fertilize the egg when it's released. Your most fertile days are the 2 to 3 days before and including ovulation.

How to find it

• Estimate from cycle length using the Fertile Window Calculator and Ovulation Calculator
• Watch cervical mucus - clear, slippery, egg-white texture signals peak fertility
• Use ovulation predictor kits - detect the LH surge 24 to 36 hours before ovulation
• Track basal body temperature - confirms ovulation after it happens

Why it matters

• Trying to conceive: time sex to the fertile window, especially the days just before ovulation
• Avoiding pregnancy: the fertile window is when to use protection (note that fertility-awareness methods require careful tracking and rules)

Ovulation isn't always on day 14, so the fertile window shifts with your cycle.

Read ovulation symptoms for how to pin it down.

Femora predicts your fertile window from your own cycles and sharpens as you log more.