Ovulation calculator

Estimate your fertility window with our simple ovulation calculator

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

TasIVF’s Ovulation Calculator will help you understand your ‘fertile window’ – or your window of opportunity to fall pregnant during an average menstrual cycle. You should be having sex every couple of days during your fertile window to maximise the chance of conception.

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. A woman’s menstrual cycle 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 use the ovulation calculator

Simply select your usual cycle length from the dropdown box and then choose the date on the calendar when your last period started. With this information, our ovulation calculator estimates your next fertility window (and the next one after that).

How to calculate your fertile window / How to calculate ovulation

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.

Remember that your best chance of success is from intercourse just before you ovulate – 1-2 days before you ovulate.

What are the common signs of ovulation?

Ovulation differs from woman to woman, but here are a few common symptoms of ovulation to look out for:

  • Your cervical mucus will become more stretchy and clear, like an egg white (this change makes it easier for sperm to swim to the egg).
  • Your basal body temperature will rise slightly and stay elevated during your most fertile days.
  • You might experience nausea and headaches while you ovulate due to changes in your levels of oestrogen and progesterone.
  • Your cervix may become higher, softer, and more open.
  • Light brown spotting or discharge.
  • Mild pain in the pelvis or lower abdominals.
  • Increased sex drive.
  • Increased sensitivity to smell and taste.
  • Sore or tender breasts.

What if I have irregular menstrual cycles?

If you have irregular menstrual cycles or your cycle length varies from month to month, it can 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.

Don’t worry if you have recently stopped using oral contraceptive pills, IUDs or implants, even for a long period of time - this will not cause infertility. If your periods are irregular once you stop using contraception you should consult your GP.

A typical menstrual cycle will range between 23 to 35 days. Speak to your GP or a fertility specialist if you are concerned about variations in your menstrual cycle. 

How long should I try to get pregnant 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.

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

Other helpful resources:

Get Expert 'Planning for Pregnancy' Advice »
Learn more about TasIVF »

Do you have irregular periods? Listen to Dr Emily Price, one of TasIVF’s leading fertility specialists, as she explains how to get pregnant with irregular periods.

Getting pregnant with irregular periods