If you're trying for a baby, knowing when you're ovulating can seem a bit confusing especially if your periods aren't regular. To stand your best chance of conceiving, you need to use an ovulation date calculator.

An average woman's menstrual cycle is 28 days but cycles can range from 22 days right up to 36. Your cycle begins on the first day of your period and continues up to the day before you start your next one.

Follow these three steps to calculate your ovulation date and find out when you're likely to be most fertile.

Step 1

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.

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

Your cycle length is 33.

Step 2

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

Step 3

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

First day of last period = 3rd February 2008
Cycle Length = 33
Ovulation (19 days later) = 22nd February 2008
Most fertile (18-20 days later) = 21st and 23rd February 2008

Once you know your ovulation date, as a rule, you are most fertile the day before, during and the day after. However, because sperm can survive for up to seven days in the right conditions you could be fertile before and after these days.

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

- Print out and keep version

Where next?
- 10 things you need to know about ovulation
- Recognising when you're most fertile
- Eat to get pregnant
- Facts about infertility
- Are you pregnant? Find out what symptoms to look for
- Are fertility home testing kits worth the money? Find out the facts

By Vicky Woollaston

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