Usually about 14 days before your next period, so around day 14 of a 28-day cycle.

How long is the fertile window?

About six days: the five days before ovulation plus the day itself.

Can I get pregnant outside the fertile window?

It's much less likely, but cycles vary, so timing isn't a reliable contraceptive.

Ovulation and Your Fertile Window

Published 10/22/2025 · 2 min read · Health calculators

Sofia Nunes — Health & wellness writer at Allin

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In short

Ovulation is when an ovary releases an egg — usually about 14 days before your next period. The fertile window is the roughly six days ending on ovulation day, because sperm can survive up to five days and the egg about one. In a regular 28-day cycle that's around days 10–15. Cycle length varies, so the timing shifts from person to person.

Ovulation is usually 14 days before your next period, and the fertile window spans about six days. Here's how it works and how to estimate yours.

What ovulation is

Ovulation is the moment an ovary releases a mature egg, triggered by a surge of luteinising hormone. It usually happens about 14 days before the next period starts — note, before the next one, not simply in the middle of the cycle. That distinction matters: the second half of the cycle, after ovulation, is fairly fixed at around 14 days, while the first half is what stretches or shrinks when cycles are longer or shorter.

The fertile window

You can only conceive around ovulation, but the window is wider than the single day the egg is available. Sperm can survive in the body for up to about five days, and the egg lives for around 24 hours after release. Put together, that gives a fertile window of roughly six days: the five days before ovulation plus ovulation day itself. Intercourse in the two or three days just before ovulation tends to give the best chance.

Estimating your window

The simplest estimate works backwards from your next expected period: subtract 14 days to find your likely ovulation day, then count back another five for the start of the window. On a 28-day cycle that lands ovulation near day 14 and the fertile days around days 9 to 14. The catch is that it only works if your cycle is regular — so tracking the length of several cycles first makes any estimate far more reliable.

Signs and better tracking

Your body gives clues. Cervical mucus becomes clear, slippery and stretchy — like raw egg white — in the fertile days. Basal body temperature ticks up slightly just after ovulation, confirming it happened. Ovulation predictor kits detect the hormone surge a day or so before. These signs sharpen a calendar estimate, and they help whether you are trying to conceive or trying to understand your cycle; they are not a reliable method of contraception on their own.

Ovulation calculatorFind your fertile window from your last period.Try the tool →

Frequently asked questions

When do you ovulate?: Usually about 14 days before your next period, so around day 14 of a 28-day cycle.
How long is the fertile window?: About six days: the five days before ovulation plus the day itself.
Can I get pregnant outside the fertile window?: It's much less likely, but cycles vary, so timing isn't a reliable contraceptive.

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This is general information, not medical or contraceptive advice. For conceiving or avoiding pregnancy, speak to a healthcare professional.

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