Ovulation calculator

Each woman's menstrual cycle is different, so getting to know your body better can improve your chances of conception.

This ovulation calculator allows you to find out when you'll be most fertile, and what your due date would be if you conceived during these times.

Ovulation calculator

What was the first day of your last period?

What is your average cycle length?

For the best chance of getting pregnant, you need to maximise the chance of a fertile egg and your partner's sperm getting together. You can only get pregnant on the few days each cycle around ovulation, when an egg is released.

When is the best time to conceive?

To increase your chances of getting pregnant, you need to maximise the possibility of a fertile egg and your partner's sperm getting together. You can only get pregnant on the few days each cycle around ovulation, when an egg is released.

How the menstrual cycle works

  • Your cycle starts on the first day of your period and continues up to the first day of your next period.
  • At the same time, eggs begin to mature in the ovary.
  • The lining of the womb starts to thicken in readiness for fertilisation.
  • During ovulation your cervical mucus becomes thinner and clearer to help the sperm to reach the released egg.
  • About 10 to 16 days before the start of your next period, an egg is released from one of the ovaries (ovulation).
  • If sperm is present at the moment of ovulation, or some time during the next 24 hours, the egg may be fertilised.
  • If the egg has not been fertilised, the egg is re-absorbed by the body, the hormone levels drop, and the womb lining is shed – the beginning of your next period.

Conception and sex

To boost your chances of conceiving, aim to have regular sex throughout your cycle so you know that there should hopefully be good-quality sperm waiting for the time that the egg is released. An active sex life is all most people need to conceive.

If you are quite sure when you ovulate each month you can give yourself the best chance of getting pregnant by having sex in the days leading up to ovulation. Continue having sex during ovulation. After this your fertile time will be over for that cycle.

How to spot the signs of ovulation

Ovulation usually happens about 10 to 16 days before the start of your next period, so  it helps to know your cycle length before you start trying to conceive.

You may never have considered when you might ovulate within your cycle, and if you have been using a hormone contraceptive such as the Pill, you won’t have had a natural menstrual cycle for a while.

As a first step, mark on your ovulation calendar the dates that you bleed during a period. You can then count how many days from the first day of your period to your next period to work out the length of your cycle.

Cervical mucus changes

The cervix secretes mucus throughout the menstrual cycle, starting off sticky white and gradually becoming thinner and clearer.

Before and during ovulation the mucus increases and becomes much thinner, slippery and stretchy. Women often compare it to raw egg white.

This thinner mucus is designed to help the sperm swim easily through it. It indicates that you are in your fertile phase, so this is the time to have sex if you want to get pregnant, but use contraception if you do not!

The last day you notice the wetter secretions is sometimes known as ‘peak day’ and for most women this occurs very close to the time of ovulation.


You can also find out about your menstrual cycle by keeping a note of your temperature each morning when you wake up. Your temperature rises by about 0.2°C when ovulation has taken place.

As it is only an indicator that you have ovulated, and doesn’t tell you when your fertile time starts, this is not very useful for most women.

Using ovulation test kits (also known as ovulation predictor kits)

Ovulation predictor kits are available from chemists and are fairly simple to use. They work by detecting a hormone in your urine that increases when ovulation is about to take place.

The simplest ovulation test kit checks for luteinising hormone (LH), which surges 24-36 hours before ovulation. This will help to identify the best two days for conception, although a woman can be fertile for a day or so before and after this time.

It is best to become familiar with your usual menstrual cycle to help figure out when you should start testing. If you have an irregular cycle then an ovulation predictor kit can help you identify the time of ovulation, but expect to use more of the test strips.

Find out more in our getting pregnant FAQs

Read more


  1. Macdonald S, Macgill-Cuerden J (2012) Mayes’ midwifery: a textbook for midwives, 14th edition, London Balliere Tindall


Hide details

Last reviewed on April 1st, 2014. Next review date April 1st, 2017.

Was this information useful?

Yes No


  • By Anonymous (not verified) on 25 May 2017 - 13:59

    Hello my last month date is 29th March and I participate unprotected sex on 19th may can I get pregnant

  • By Midwife @Tommys on 25 May 2017 - 14:11

    Hi, if you have had unprotected sex and you haven't been using any form of contraception then yes it is possible to get pregnant.
    Best Wishes x

  • By Anonymous (not verified) on 29 Apr 2017 - 20:03

    how will i if am pregnant?

  • By Midwife @Tommys on 2 May 2017 - 14:20

    If you have been having unprotected sex and your period is late it is possible that you are pregnant so the next step would be to do a pregnancy test.

    Warm regards
    Anna- Tommy's Midwife

  • By Anonymous (not verified) on 18 May 2017 - 09:31

    I missed a period by 5 days it was due on the 3rd of may I a test clear blue easy that came back as a faint positive noq started to bleed on the Sunday for 3 days finished in went to the doctors done a urine test that come back negitive on the tuestay it wasn't enough blood to fill a pad the 2 following morning I had spotted now im testing negitive now I feeling like I'm pregnant as I've had a previous pregnancy, just so confused

  • By Midwife @Tommys on 18 May 2017 - 10:29

    It can be very confusing when you have had what you think is a faint positive test but then you bleed and afterward get negative pregnancy tests, it may be that you have had a very early miscarriage. If you continue to feel pregnant then it may be advisable for you to do another pregnancy test in a few days just to see if it is still negative. If you think that you may be pregnant then the GP can always do a blood test to check for the pregnancy hormone. Thank you for your comment and we wish you all the best.

  • By Anonymous (not verified) on 1 Jun 2016 - 06:11


Add new comment