Ovulation calculator: When will I ovulate?

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  • Trying to conceive a baby can be a stressful and challenging time, especially as it can require a great deal of planning and preparation - including checking when you're ovulating.

    An ovulation calculator will help you to predict when you will ovulate. This in turn will narrow down your best window to become pregnant.

    Using an ovulation calculator is a great way to manage your fertility to predict when ovulation might happen and it also helps take away some of the confusion around tracking cycles naturally – especially if your periods aren’t regular.

    An average menstrual cycle begins on the first day of your period and continues right up to the day before you start the next one. This means it’s about 28 days on average, but they can range from 22 days right up to 36 days. If you’re struggling to conceive, it’s best not to just guess when the best ovulation date might be.

    Along with your average menstrual cycle length, you will also need to know the length of your ‘luteal phase’ to use our ovulation calculator as efficiently as possible. The luteal phase begins after ovulation and ends the day before your next period. It 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 helps you to predict when your most fertile day will be for the best chances of conception. It can also help people to monitor their signs of ovulation, so they’ll be able to recognise at what point in the cycle they’re in.

    “Some people find it reassuring to monitor signs of ovulation and feel confident they are taking control over boosting their fertility.” Dr Matthew Prior, fertility consultant and medical director at Dr Fertility says, “However, some research shows that getting too hung up on your cycle can cause more stress and 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

    This 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 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 Faris 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?

    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.

    woman checking ovulation calendar

    Credit: Getty

    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

    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 from Dr Fertility 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.

    thermometer to measure fertility and ovulation

    Credit: Getty

    “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 Ovulation Most fertile
    22 Day 8 Days 7-9
    23 Day 9 Days 8-10
    24 Day 10 Days 9-11
    25 Day 11 Days 10-12
    26 Day 12 Days 11-13
    27 Day 13 Days 12-14
    28 Day 14 Days 13-15
    29 Day 15 Days 14-16
    30 Day 16 Days 15-17
    31 Day 17 Days 16-18
    32 Day 18 Days 17-19
    33 Day 19 Days 18-20
    34 Day 20 Days 19-21
    35 Day 21 Days 20-22
    36 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?

    Young woman using phone to check for ovulation date

    Credit: Getty

    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.”

    How to track your fertility

    The best way to track fertility is through your natural fertility indicators, fertility nurse Kate Davies says, which includes checking your own temperature and cervical mucus.

    “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…