Ovulation calculator: When will I ovulate?

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An ovulation calculator can help to identify the few days of the month that are your best chance of getting pregnant. 

Using an ovulation calculator is a great way to maximise the chance of your fertile egg and your partner’s sperm getting together and to manage your fertilityIt can also help predict when ovulation might happen and to make sense of tracking your cycles – especially if your periods aren’t regular.

“Some people find it reassuring to monitor signs of ovulation and feel confident they are taking control over their fertility.” Dr Matthew Prior, fertility consultant and medical director at Dr Fertility says.

If you’re trying to conceive, it’s best to know your ovulation date. To use our ovulation calculator you need to know your average menstrual cycle and when your luteal phase begins. The luteal phase is the second half of your menstrual cycle. It starts after ovulation and ends with the first day of your period. 

An average menstrual cycle starts on the first day of your period and continues right up to the day before you start the next one. An average cycle is 28 days, but they can range from 22 days right up to 36 days. 

Your luteal phase usually lasts 12 to 16 days, with an average of 14 days for most women, so if you’re unsure we’d recommend choosing 14 days on the calculator.

What is an ovulation calculator and how does it help you get pregnant?

An ovulation calculator takes the first day of your last period and the length of your menstrual cycle to give a range of days when you may release an egg. This helps you identify your most fertile days for a stronger chance of getting pregnant.

Though, it’s worth noting that Dr Matthew Prior, fertility consultant and medical director at Dr Fertility tells us that research shows getting too hung up on your cycle can cause more stress. “It can take away the enjoyment of trying to conceive causing unnecessary pressure. If this is the case it may be a good idea to stop monitoring for a few months.” 

How to use our free ovulation calculator

Our ovulation calculator helps you identify when you’re ovulating, i.e. releasing an egg, on a certain day of your menstrual cycle. It could help you to further identify your most fertile days and so help you with conception.

Work out your ovulation date using our tool below:

Ovulation Calculator

Use our calculator to find out when you’ll ovulate and when your due date is!

What was the first date of your last period?




How many days does your cycle last?

How long is your luteal phase?

Calculate Ovulation

Your ovulation date

Your due date

As with most ovulation tools, be aware that the dates given are an estimate and as Mr Raef Faris from the Lister Fertility Clinic, says, they can’t guarantee the ovulation date will be 100 per cent accurate. 

If you conceive outside of your ovulation dates for example, this will impact your due date. If you have any doubts, it’s best to contact your GP, especially as there are a whole number of factors from age to conditions like endometriosis that can affect fertility.

Calendar apps are also a way to track period dates and cycle lengths to predict when you might ovulate, Fertility Nurse Kate Davies from Dr Fertility says. “This is usually estimated to be around the middle of your cycle. However, it is well documented in the research that even having a regular 28-day cycle doesn’t mean you will always ovulate on day 14.

“Therefore, using and relying solely on a calendar App can actually be misleading. I encourage women to consider observing their natural fertility indicators (temperature and cervical mucus) and using this information to become empowered and knowledgeable on their cycle, fertility and ovulation.”

Doctors, such as Mr Raef Faris from the Lister Fertility Clinic, also warn that “[fertility calculators] are not very accurate and may result in missing the appropriate window for conception.”

However, if you’re struggling to conceive and looking to identify potentially your most fertile period, then it is worth trying a calculator like this, to see if it makes a difference.

What is an ovulation calendar and how do you use one?

An ovulation calendar is a tool to calculate your most fertile days, it can help you to track your menstrual cycle. After working out the ovulation date using the calculator, many couples turn to an ovulation calendar (otherwise known as a fertility calendar) to figure out the days of the month where they’re most likely to conceive if they have sex.

It works as sperm can live in the body for up to five days after sex, so conception can occur even if you’ve had sex four or five days before ovulation begins. The fertility window is normally around six days, as that is the amount of days that the egg and sperm can survive. To figure out this fertile period, plot on your menstrual cycle on a calendar then count back 14 days from the expected last day of your next cycle. This will be your most fertile day.

Alternatively, there are a number of apps that will do this for you – such as Clue.

When will I ovulate? How to work out your ovulation date

Ovulation happens about 14 days before your period starts. So, if your average menstrual cycle is 28 days, you ovulate around day 14, and your most fertile days are days 12, 13 and 14. If your average menstrual cycle is 35 days ovulation happens around day 21 and your most fertile days are days 19,20 and 21. 

By using the ovulation calculator above, you can work out your ovulation date. But there are other ways to work out when you might be ovulating if the calculator doesn’t seem suitable, according to our experts.

“There are a few methods used mostly depending on the hormone surge that occurs prior ovulation.” Mr Faris says, “This includes temperature rise, cervical mucus and urine ovulation”

He warns, however, “They may not be accurate as some women may not show signs of ovulation but would have ovulated already. The best advice would be trying naturally (every 2-3 days) soon after the period is over till day 20 of the cycle, but it could be extended (depending on the length of the cycle).”

While Dr Matthew Prior explains, “Some women can tell if they are ovulating where others can’t. When you ovulate, you may notice a change in your discharge and a slight increase in temperature or change in urine ovulation predictor kits.

“While these are all useful tools there is no evidence to suggest monitoring your cycles improve your chance of getting pregnant. This is because sperm can survive for several days in the reproductive system so as long as you are having sex every couple of days it is not important to get the timing to coincide with ovulation.” 

But if you want to try it, here’s a step by step guide to working out your ovulation date…

Step 1: Your menstrual cycle

When your next period starts, make a note of the date. The following month, when your period comes again, make a note of this date, then count the days in between. This will give you your cycle length. You may need to do this for more than one month and take the average, especially if your cycle isn’t regular. Remember also that coming off the Pill will reveal your true menstrual cycle.

Period starts = 1st January Next period starts = 3rd February
Days in between (including 1st Jan but not 3rd Feb) = 33 days.

This means your menstrual cycle length is 33.

Step 2: Your fertile dates

Using our ovulation calendar, find the right number in the menstrual cycle length column (33 for the above example) and read across for your ovulation day and most fertile days.

Cycle length
Most fertile

Day 8
Days 7-9

Day 9
Days 8-10

Day 10
Days 9-11

Day 11
Days 10-12

Day 12
Days 11-13

Day 13
Days 12-14

Day 14
Days 13-15

Day 15
Days 14-16

Day 16
Days 15-17

Day 17
Days 16-18

Day 18
Days 17-19

Day 19
Days 18-20

Day 20
Days 19-21

Day 21
Days 20-22

Day 22
Days 21-23

Step 3: Your ovulation date

Work out your ovulation and most fertile dates. For the below example:

First day of last period = 3rd February 2021
Cycle Length = 33
Ovulation (19 days later) = 22nd February 2021
Most fertile (18-20 days later) = 21st and 23rd February 2021

Once you know your ovulation date, as a rule, you are most fertile the day before, during and the day after.

N.B. These figures are based on averages and should be used as a guide only. Days and dates may differ from person to person.

I have irregular periods, when will I ovulate?

No matter the length of her period, every woman ovulates about 14 days before her next period. So, if you have a 28-day cycle, you’ll ovulate on day 14, and if you have a 32-day cycle, you’ll ovulate on day 18.

Mr Faris advises that the ovulation date in this case could vary, so “it would be useful to try regularly after the period and not to rely on the ovulation kits.” This is because, as Dr Matthew Prior says, “Having regular periods is the best sign of ovulation. In fact, fertility specialists may not even advise bloods to check if ovulation has happened because regular cycles are a sure sign of ovulation.”

Fertility tracking: How to do it

The best way to track fertility is through your natural body indicators. Fertility nurse Kate Davies says that this includes checking your own temperature and cervical mucus.

She goes on to add; “These fertility indicators, used together, can give you a reliable indication of when you are in your fertile time. You can choose to use systems to help you interpret your physiological data such as Apps and fertility monitors and some women also choose to use ovulation predictor kits to help identify when ovulation is about to occur.” 

Have a look at some of these easy tools to find out your ovulation date and fertility window…

The post Ovulation calculator: When will I ovulate? appeared first on GoodtoKnow.

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