Ovulation Calculator

What is a fertile window?

If you’re trying to fall pregnant, the timing of when you and your partner have intercourse is critical.

Your fertile window refers to the most fertile days in your menstrual cycle which give you the highest chance of conceiving.

If you are trying to fall pregnant, the timing of when you and your partner have sex is critical. Our online ovulation calculator can help you understand your fertile window or your window of opportunity to fall pregnant during a normal menstrual cycle. You should be having sex every couple of days during your fertile window.

For our Ovulation Calculator to be the most accurate and useful, you’ll need to keep track of the dates of your recent menstrual periods. 

Your cycle length is the number of days between the first day of bleeding of one period, and the first day of bleeding of the next. This can vary from 23 to 35 days, and 28 days is about average. If you have irregular menstrual cycles, calculating your ovulation date can be more difficult, but we suggest going by your shortest period date to ensure you don’t miss your ovulation date. Ovulation urine tests can give you some idea of your fertility window, or you might find further advice from your GP or fertility specialist useful.

How to calculate your fertile window

To calculate your fertile window, you need to determine what day you ovulate. To do this, you need to know the length of your menstrual cycle (which tends to vary from 23 to 35 days).

The length of your menstrual cycle is the number of days from the first day of bleeding in your last period, to the first day of bleeding in your next. From this figure, subtract 14 days from the end of your current cycle to determine the approximate day you ovulate.

What if I have irregular menstrual cycles?

If you have irregular menstrual cycles, or your cycle length varies from month to month, it will be difficult to calculate your ovulation date. Ovulation urine tests or ovulation tracking may be useful, and you should consider seeking further advice from your GP or a Fertility Specialist.

When am I most fertile?

If you are trying to fall pregnant, the timing of when you and your partner have intercourse is important. The most fertile time in your cycle are the days leading up to ovulation, just before the egg is released from the ovary when the cervical mucus allows sperm to pass through the cervix and into the uterus and fallopian tubes. Sperm has the ability to live for 2–3 days in the cervix, uterus and tubes awaiting arrival of the egg. The egg is able to be fertilised in the 24 hours after release from the ovary.

To optimise your chances of conceiving, it is therefore recommended you have unprotected intercourse every two to three days in the lead up to ovulation. If you wait until you have ovulated before you have intercourse, it is most likely that you will have missed the opportunity for conception that month

About conception

For a naturally conceived pregnancy to occur it requires normal egg production (ovulation) by the ovaries, normal healthy sperm both in structure (shape or morphology) and the ability to swim (motility), and normal fallopian tubes and uterus.

During intercourse the sperm will make their way through the woman's cervix into the uterus and then along the fallopian tubes. This is where the sperm will encounter an egg that has been released from the female ovary. Conception starts at the moment of fertilisation when a sperm penetrates the outer shell of the egg and an embryo is subsequently formed.

Over the next four to six days the embryo moves down the fallopian tube to the uterus and implants in the lining of the uterus where it will hopefully continue to grow.

3 steps for conception

Most couples have spent years trying not to fall pregnant. So, when you decide to stop using contraception (pill control) and start trying for a baby, it helps to get a little advice on where to start.

There are three important ways you can improve your chances of falling pregnant naturally:

  1. Understand your pregnancy window, and determine the best time in your cycle to have intercourse.
  2. Improve your health, diet and lifestyle – for both partners.
  3. See a GP to ensure you are (both) in good health.
Bulk billed ovulation cycle tracking

Ovulation cycle tracking can help you confidently understand your fertile window by tracking your hormone cycle and detecting the hormone surge associated with ovulation. Read more about ovulation cycle tracking...

Health advice if you are trying to conceive

If you are trying to conceive, we recommend you and your partner get checked by your GP to ensure you are in good physical health. This typically involves blood tests to help with a review of your general health and a check of your current medications. For women your doctor will likely make sure you are up-to-date on your pap smear tests, rubella and advise you to start taking folic acid.

For both the male and female it is time to commit to a healthy lifestyle:

  • Quit smoking and any recreational drug use.
  • Optimise your weight for a healthy BMI.
  • Review your diet and alcohol intake, and reduce if necessary.
  • And ensure you exercise regularly.

Learn more about preparing your body for pregnancy »

How long should I try for, before seeking specialist advice?

It is recommended that you consider seeking professional advice after trying to conceive naturally without success for 12 months if you are under 35 years-old or after 6 months if you are over 35.

fertility specialist can conduct some simple fertility tests to find out what’s happening, explore all your options and help you fall pregnant sooner.