Getting pregnant

How to work out when you ovulate

By Nine Moons EditorialMedically reviewed by Professor Dr FarhatUpdated 9 Oct 20266 min read

Quick answer

Ovulation usually happens about 14 days before your next period starts, so it moves with your cycle length. You're most fertile in the 5 days before ovulation and on the day itself. Having sex every 2 to 3 days through the cycle covers this window without needing to time it exactly.

Key facts

Fertile window	About 6 days: 5 before ovulation plus ovulation day
Ovulation day	About 14 days before your next period
Egg lifespan	About 12 to 24 hours
Sperm lifespan	Up to 5 days
See a doctor	After 12 months of trying (6 months if you're 35 or over)

How ovulation timing works

Your cycle has two halves. The first half, before ovulation, varies from woman to woman. The second half, after ovulation, is more fixed at about 14 days. That's why ovulation is calculated backwards from your next period, not forwards from the last one.

28-day cycle: ovulation around day 14
32-day cycle: ovulation around day 18
25-day cycle: ovulation around day 11

Your fertile window is the 5 days before ovulation plus ovulation day. In a longer cycle it moves later; in a shorter one, earlier.

Use our ovulation calculator to see your likely fertile days for the next three cycles.

Signs you may be ovulating

Cervical mucus becomes clear, slippery and stretchy, like raw egg white.
Ovulation test strips detect the rise in LH hormone 24 to 36 hours before ovulation.
Basal body temperature rises slightly after ovulation. This confirms it has happened, so it helps you learn your pattern over several months.
Some women feel a one-sided twinge in the lower tummy.

If your cycles are irregular

If your cycle length changes by more than a week from month to month, calculators are less reliable. Ovulation strips and tracking mucus will help more. Irregular cycles can be a sign of polycystic ovary syndrome (PCOS), which is common in South Asian and Middle Eastern women, so mention it to your doctor.

Getting ready for pregnancy

Start folic acid 400 micrograms a day now, ideally 3 months before trying. See our first trimester guide for who needs a higher dose.
Check your rubella immunity and any long-term medicines with your doctor.
Stop smoking and alcohol. Keep caffeine moderate.

When to see a doctor

See a doctor if you've been trying for 12 months, or 6 months if you're 35 or over. Go sooner if your periods are very irregular or absent, very painful, or if either partner has a known fertility problem. Fertility checks look at both partners.

Frequently asked questions

Is ovulation always on day 14?

No. Only in a 28-day cycle. It's about 14 days before your next period, so it changes with cycle length.

Can I get pregnant right after my period?

Yes, especially with a short cycle, because sperm can live up to 5 days.

Do ovulation apps work?

They estimate. Combine them with ovulation strips or mucus changes for better accuracy.

Sources

NHS: Trying to get pregnant
NICE CG156 Fertility problems
ACOG: Fertility awareness

General information, not medical advice. Medical disclaimer · How we review content

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