Ovulation calculator

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Ovulation calculator chart
If you're trying to get pregnant, 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 calculator.

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

Use our free ovulation calculator to find out when you're ovulating over the next six months.

Work out your ovulation date using our tool below

Alternatively, follow these three steps to calculate your ovulation date and find out when you're likely to be most fertile

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.

Your menstrual cycle length is 33.

Step 2: Your fertile dates

Using our ovulation calender, 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 lengthOvulationMost fertile
22Day 8Days 7-9
23Day 9Days 8-10
24Day 10Days 9-11
25Day 11Days 10-12
26Day 12Days 11-13
27Day 13Days 12-14
28Day 14Days 13-15
29Day 15Days 14-16
30Day 16Days 15-17
31Day 17Days 16-18
32Day 18Days 17-19
33Day 19Days 18-20
34Day 20Days 19-21
35Day 21Days 20-22
36Day 22Days 21-23

Step 3: Your ovulation date

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.

Continued below...

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.


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