Ovulation Calculator

What exactly does your fertile window mean and can you predict when you're most fertile? You can if you can estimate when you're likely to ovulate. This is because you're fertile in the days leading up to ovulation, as well as the day itself. To take the guesswork out of fertility, our ovulation calculator will tell you when you’re most likely to conceive over the next six months.

What is the fertile window?

The few days in your cycle when you can conceive is known as your fertile window and the best time for trying for a baby. The fertile window includes the days leading up to ovulation and the day of ovulation itself. Ovulation is when your ovaries release an egg for sperm to fertilise. Sperm can live in your body for a few days, so you may conceive if you have sex in the days leading up to ovulation.

You usually ovulate two weeks before your period. So, to find out your fertile window and 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). Our calculator will work out when your cycle will end, and count back two weeks to estimate when you may ovulate. It will then create a personalised fertility calendar showing your full fertile window each month for the next six months.

The ovulation calculator 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 cycles are irregular, you may have trouble pinpointing your day of ovulation based on this calendar alone. Find out about ovulation predictor kits (OPKs).

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 else can I tell when my fertile window is?

Our calculator will estimate the dates up to and including ovulation, which is when you're most fertile. But you may also want to check for signs and symptoms that can give you a clue to your fertile window. These include:

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 you or your partner often work away. But for many couples, timing and charts can be stressful and take the spontaneity 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.

Give yourselves the best chances of getting pregnant with our nine tips for quick conception.