Ovulation calculator

Knowing the signs of ovulation and using an ovulation calendar can help you to work out the best time to get pregnant. Once you can spot your ovulation symptoms and know your cycle, you will be able to identify the time when you're at your most fertile. This means that when you're trying to get pregnant, you can concentrate your baby-making efforts on the days when the odds are in your favour.

How do you know when you are ovulating?

Use our quick and easy ovulation calculator tool below to find out the days each month that you are at your most fertile.

You don't need to know how to calculate ovulation – simply enter the date your last period started and the length of your menstrual cycle (this is the number of days from the start of one period to the day before the next one). The calendar below will then highlight the dates when you're most likely to conceive.


You're at your most fertile during the days leading up to ovulation, and on the day itself. To maximise your chances of conceiving, use our calculator to work out your most fertile dates over the next six months.

Enter the date your last period started

How long is your menstrual cycle?

My Ovulation Calendar

First day of your period

Most fertile days

When do you ovulate?

Contrary to what some biology textbooks may tell you, most women do not ovulate like clockwork 14 days before their period. Menstrual cycles can last between 24 and 35 days, and ovulation can happen anywhere between 10 and 16 days before menstruation begins.

If your periods are irregular (if your cycle length varies each month, or is consistently shorter than 24 days or longer than 35 days) it might be a bit trickier to work out when ovulation occurs – but it's not impossible! There are many potential reasons for irregular cycles, including things like stress, certain medications and being underweight, so it's a good idea to visit your GP to discuss this when you start trying for a baby.

Ovulation symptoms

Look out for signs of ovulation such as changes in your body temperature, cervix and cervical mucus and how you feel in general. Nearer to ovulation, your cervical mucus will take on a stickier, almost stringy quality, and will look whiter than usual. You might find you get sore breasts, too, and experience slight lower abdominal pain on one side. Keeping track of any changes throughout the month, by recording your basal body temperature, can help you recognise your own symptoms around ovulation and better understand the length of your cycle, and at which point you are most fertile.

Ovulation tests

If you find the physical signs hard to spot, you might also want to try an ovulation test. Ovulation predictor kits (or OPKs) make it easier to zero in on your fertile window and do away with some of the head-scratching – especially if you're not sure how long your cycle is. There are two types of tests available – one that measures the level of luteinising hormone (LH) in your urine, and one that measures the amount of salt in your saliva. If you opt for the wee test, you're looking for a surge in LH, which means you're a couple of days away from ovulation and in prime baby-making time. It's best to take the test around lunchtime, rather than first thing in the morning, and try not to drink too much water in the few hours before, as this could dilute your urine and make it hard to detect the LH.

If you choose the saliva-based tests, you'll need to use a small microscope and some slides to check the salt in your saliva (lab coat optional). You'll need to lick the slide and then let it dry. If it dries clear, you've not reached your fertile window. If it dries with a little patch of salt residue that looks a bit like a fern leaf, you're entering the most fertile time in your cycle. It's important to note that saliva tests don't necessarily work perfectly for all women, and can be disrupted by external factors such as eating, drinking and smoking, so it's best to use it in conjunction with the ovulation calculator.

Best time to get pregnant

It's recommended that, if you’re trying to get pregnant, you should be having sex throughout your cycle in order to increase your chances – every other day is the optimum. However, the best time to conceive is in the two days before ovulation (usually days 12 to 14) in preparation for the egg being released.

Before you start, find out how you can prepare your body and mind for conception throughout the month, to improve your chances of getting pregnant in your fertile time. There are also important lifestyle changes your partner may need to take into account in order to keep his sperm count as high as possible. After the 28 days of tracking, testing and Doing the Deed, it's time to grab a pregnancy test and keep your fingers crossed for a BFP.

calendar show date of ovulation