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Ovulation Calculator – Find Out The Best Time To Try & Conceive


Trying to conceive? Are you wondering “How do I calculate my ovulation day?”. Do you want to know the fertile window of your menstrual cycle? Great news! Our ovulation calculator works out the the best time for you to try and conceive.

Having a good understanding of your fertility is essential when you are trying to conceive. The more information you have about your body, your cycle and your fertile window, the greater your chances of conception success.

The only time a woman can technically conceive is during the fertile window of the menstrual cycle. The fertile window lasts six days in total, five days before ovulation through to the day of ovulation. This window will vary depending on the individual’s cycle.

However, the likelihood of becoming pregnant is significantly increased if you have intercourse in the three days leading up to and including ovulation. During these three days your body is primed to conceive.

Note: The calculations provided are only estimates based on averages and should be treated as such. You should consult a fertility specialist if you require a proper diagnosis.

Ovulation Calculator – Input Your Details

  • Your fertile window is between days:
  • Your most fertile time is between days:
  • Your predicted ovulation day is:
  • If you conceive within this timeframe, your estimated due date will be .
The Ovulation Calculator is one tool in your armoury. There are other methods of checking your fertility potential and you should make use of them all.
Read our article How Fertile Am I? to make sure you have all the information you need.

How Do I Calculate My Ovulation Day?

To calculate your ovulation day, and the best time for you to try and conceive, you need to know both the first day of your last menstrual cycle, and the number of days in your menstrual cycle. Armed with this information, fill in the ovulation calculator, above, and click ‘Calculate!’

If you don’t know the number of days in your menstrual cycle, leave it as the default of 28 days, which is considered a standard cycle.

Please remember that any estimation of ovulation date is just that – an estimation.

How Does The Ovulation Calculator Work?

Our ovulation calculator uses the first day of your last menstrual cycle, and the number of days in your menstrual cycle to work out your predicted ovulation day. The ovulation calculator will also determine your most fertile window – the ideal time to conceive.

How Accurate Is The Ovulation Calculator?

Our calculator uses the same method that doctors and fertility specialists use for estimating your ovulation date.

How Can I Know My Ovulation Day If I Have An Irregular Menstrual Cycle?

Our ovulation calculator works out your ovulation date by assuming that your menstrual cycle is regular. If you have an irregular menstrual cycle, it can be much more difficult to work out your ovulation date.

If you have an irregular menstrual cycle, you should visit a doctor or fertility specialist who can use alternative methods to work out your ovulation date and most fertile window.

How Do You Know If You Are Ovulating?

There a few different ways you can tell if you are ovulating. You can use a thermometer to monitor your body temperature – your basal body temperature will rise slightly after ovulation happens.

Try paying attention to the changes in your body as these can indicate ovulation. Changes can include tender breasts, bloating, and you may also notice your cervical mucus is more slippery, and clearer during ovulation.

An ovulation predictor kit can also measure the hormone levels in your urine and if levels of hormones are higher than normal, this can be used to determine your ovulation period.

How Can I Improve My Chance Of Getting Pregnant?

Your chance of getting pregnant can be affected by many factors, including diet, weight and exercise. Many couples are so focussed on the end goal of having a baby, they can sometimes forget that it’s important to look after themselves. To find out more, read our article Are You Baby Fit?

It’s not unusual for it to take at least 9 months for a couple to get pregnant naturally. However, if you’ve been trying for 12 months, it would be useful to visit a fertility clinic to find out if anything might be preventing you from conceiving.

Around 1 in 7 couples experience issues conceiving. Have you been trying for a baby for more than 12 months? Find out more about the factors that may be affecting you in our article The Most Common Causes Of Infertility.