How can I tell when I ovulate?

Ovulation is the part of your menstrual cycle when your ovaries release an egg. It’s the most fertile time in your cycle. It usually happens in the middle of your menstrual cycle and lasts 12–14 hours.

It's helpful to predict when you’ll ovulate if you're:

  • not using any contraception

  • using a fertility app or natural family planning to avoid pregnancy

  • trying to get pregnant

Ovulation date and emergency contraception

If you want to use the non-hormonal coil as emergency contraception, you’ll need to check the earliest date you’re predicted to ovulate. The coil can only be fitted before, or up to 5 days after, this date.

Signs of ovulation

Some people notice signs that they’re ovulating during that stage of their cycle. Some people get ovulation pain, like a cramp or ache on one side of their tummy or lower back. Some report a sort of 'ovulation sickness' due to changing hormones (this might feel like a slight nausea or queasiness similar to mild morning sickness – but if your nausea is severe, or you vomit, you should speak to your doctor).

Other signs of ovulation include:

  • changes to your discharge when your cervical mucus (fluid produced by your cervix) becomes slipperier, wetter and clearer during ovulation

  • a slightly increased body temperature – you’ll probably only notice this if you use a very accurate thermometer

  • bloating

  • breast tenderness

  • increased sex drive

Monitoring your discharge and temperature is a key part of using natural family planning methods.

Predict your next ovulation date

You can never be 100% sure about exactly when you will ovulate. Even if you track it on an app and have a regular cycle, it can happen a few days before or after your predicted date. But you can get an idea of when it happens, even if you don't get any symptoms. It can be complicated to work out, so you might prefer to talk it through with a health professional.

If you use an app to track your period, it might also predict your ovulation dates. If not, use the date of your period that you’ve recorded in the app to predict it yourself.

Ovulation usually happens 12-16 days before your period starts, so if you have a regular cycle you might be able to work out when your next ovulation will be. To calculate it yourself:

  1. Work out how many days are in your typical menstrual cycle. To do this, count the days between the first day of your period and the first day of your next one. As you’re looking for your earliest possible ovulation date, you want to use your shortest cycle for this. For our example, we’ll say this works out as 27 days.

  2. Take 14 days away from this number to get your earliest predicted ovulation date. So in our example, we’d take 14 from 27. This would leave 13 days.

  3. Once you know which day of your cycle you’re predicted ovulation is, you can work out the date you’ll likely ovulate in this cycle. Using the first day of your period as day 1 of your cycle, count to the right day for your ovulation. In our example, we’ve predicted ovulation as day 13. If our period started on the 2 December, we’d count forward 13 days until the 14 December. This would be the earliest predicted date of ovulation.


Reviewed by Helen Burkitt. Senior Sexual Health and Contraception Nurse
Last updated at: 22 February 2024
Published on: 21 November 2022