21/08/2014 17:22 BST | Updated 20/05/2015 10:12 BST

Ovulation Calculator: When Am I Most Fertile?


An ovulation calculator can help you pinpoint the best days to try for a baby, based on your menstrual cycle.

If you're planning on becoming pregnant, having a fertility calendar is a really useful way of visualising your ovulation cycle across the month or months to come.

One in six couples in the UK will experience problems conceiving, so it can't hurt to maximise your chances by getting to grips with the biology behind fertility.

And if you or your partner are currently on tight schedules and have limited time for 'making babies' sex, an ovulation calculator can be invaluable when it comes to organising your love life!

How does an ovulation calculator work?

Every month, a woman's ovaries release an egg, which travels towards the womb via the fallopian tube. The womb lining thickens in preparation for a potential pregnancy. As you probably know, a period occurs when this unneeded womb lining disintegrates if the egg remains unfertilised.

The egg doesn't survive more than 24 hours after ovulation, so fertilisation must take place in this narrow time frame.

However, you don't have to start timing sex sessions to the hour! Sperm can survive for up to seven days inside the vagina. This means your peak fertility period will include five days before ovulation as well as the day itself.

As ovulation usually takes place between 12 and 14 days before your period is due, an ovulation calculator can take the date of your last period and length of your normal cycle and use this data to show you your most fertile days in the months to come.

Where can I find a reliable ovulation calculator?

If you're interest in consulting a fertility calendar, the NHS has a great one. It shows you your fertile days for the next eight months, as well as showing you what your due date would be were you to conceive in that time frame.

What other factors might be affecting my fertility?

Drinking, smoking and being over or underweight are all known factors which negatively influence a woman's chance of conceiving, so it's best to follow a healthy lifestyle and eat well to increase your chances.

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