Ovulation Calculator

Our ovulation calculator will tell you when you’re most likely to be fertile over the next six months. To increase your chances of getting pregnant, just tell us the first day of your last period and how long your cycle usually lasts (between 20 and 45 days). We'll create a personalised ovulation calendar that shows you exactly when you're most likely to ovulate, and when you'll be most fertile, over the coming months.

What is ovulation?

Ovulation is when your ovaries release an egg each month. This usually happens about two weeks before your period starts.

Once an egg has been released, it's ready to be fertilised. When you have sex, sperm can live inside your body, waiting for an egg to be released, for up to a week. So having sex in the days before ovulation, and on the day you ovulate, gives you the best chance of getting pregnant.

Learn more about ovulation and how your menstrual cycle works.

How does the ovulation calculator work?

Most women ovulate about two weeks before the first day of their period. Our calculator works out when your cycle will end, and counts back two weeks to estimate when you may ovulate. It then shows your full fertile window (the days leading up to ovulation, as well as the day itself). This is the best time of the month for you to have sex if you're trying for a baby.

The ovulation calculator also shows you all your upcoming fertile days, and when your baby will be due if you do conceive. So you'll have all the information you need to start planning your pregnancy.

NOTE: This tool provides approximate dates only and assumes a regular menstrual cycle. If your periods are irregular, you may have trouble pinpointing your day of ovulation based on this calendar alone. Find out about ovulation predictor kits (OPKs).

How will I know when I'm most fertile?

You will be fertile in the days leading up to ovulation, as well as the day itself. Our calculator will give a good estimate of when this might be, but you may also want to check for signs and symptoms of ovulation, such as:

Basal body temperature
Your basal body temperature (BBT) is your temperature first thing in the morning. Many women see a spike in their temperature shortly after ovulation, so this can be a sign that you've ovulated. Learn more about charting your BBT.

Cervical mucus
Cervical mucus (CM) is the natural vaginal discharge that most women produce. The colour and texture can change throughout the month. Around the time of ovulation, your cervical mucus may be clear and slippery, a bit like raw egg white. See what fertile cervical mucus looks like.

Changes to your cervix
Throughout the month, your cervix changes in position and texture. This can also give you some indication of when you ovulate. Around the time of ovulation, the cervix is often said to be short, high, open and wet (SHOW). Find out what this means in our expert guide to checking your cervix for ovulation.

Should I only have sex when I'm most fertile?

Planning sex for your fertile window may be helpful if you find it difficult to have regular sex, for example, if your husband or you are often away on work trips. But for many couples, timing and charts can be stressful and take the spontaneity and joy out of sex.

In general, simply having sex every two to three days throughout your cycle will give you the best chance of conceiving. That way, no matter when you ovulate, there will be sperm ready and waiting to fertilise your egg as it's released.