Ovulation: Signs, Timing and How to Know When You're Most Fertile

Ovulation is when one of your ovaries releases an egg. The egg survives for about 12 to 24 hours, while sperm can survive up to 5 days in the reproductive tract. Knowing when you ovulate helps you time intercourse when you're trying to conceive.

When does ovulation happen?

Ovulation typically occurs about 14 days before your next period starts. In a 28 day cycle, that's around day 14, but in a 32 day cycle, it's closer to day 18, and in a 24 day cycle, around day 10.

The phase after ovulation is fairly constant at 12 to 16 days; it's the phase before ovulation that varies. That's why counting from your last period alone is only an estimate.

The fertile window

You can get pregnant from intercourse in a 6 day window: the 5 days before ovulation and the day of ovulation. A classic study found the chance of conception is highest when intercourse happens in the 1 to 2 days before ovulation.

Use our ovulation calculator to estimate your fertile window.

Signs of ovulation

Cervical mucus changes

As ovulation approaches, rising oestrogen makes cervical mucus clear, slippery and stretchy, like raw egg white. This helps sperm swim. After ovulation, it becomes thicker or dry.

Ovulation predictor kits

These urine tests detect the surge in luteinising hormone (LH) that happens 24 to 36 hours before ovulation. A positive test means the next two days are your most fertile.

People with PCOS may have persistently high LH, which can make these kits less reliable.

Basal body temperature

Your resting temperature rises by about 0.3 to 0.5°C after ovulation and stays up until your period. Take your temperature with a sensitive thermometer every morning before getting out of bed. This confirms ovulation has happened but doesn't predict it in advance: it's most useful for understanding your pattern over a few cycles.

Other signs

Some people notice mild one sided pelvic pain (mittelschmerz), breast tenderness, light spotting or increased sex drive around ovulation.

Tips for trying to conceive

• Have sex every 2 to 3 days throughout the cycle, rather than only on predicted days: this takes the pressure off and covers the window.
• Start folic acid (400 mcg a day) at least one month before trying, to reduce the risk of neural tube defects.
• Get to a healthy weight, stop smoking and limit alcohol, for both partners.
• Check your thyroid and treat conditions such as hypothyroidism.
• Avoid lubricants that aren't labelled "fertility friendly".

When to see a doctor

• After 12 months of regular unprotected sex if the woman is under 35.
• After 6 months if she is 35 or older.
• Sooner if periods are very irregular or absent, if either partner has a known fertility problem, or if there's a history of pelvic infection, endometriosis or surgery.

Fertility evaluation involves both partners: male factors contribute to around half of infertility cases.

Think you might already be pregnant? Read about the early signs of pregnancy.