Men’s guide to getting the timing right

Apart from being healthy, what might help you get pregnant? Sex! (Or intercourse at the right time, to be technical about it.)

The 'fertile window' is when you should be having lots of sex if you want to conceive.

The fertile window

We’re talking about the days in a woman’s menstrual cycle when pregnancy is possible. The ‘fertile window’ depends on the length of a woman’s cycle, this varies between women.

Pregnancy is technically only possible during the five days before ovulation through to the day of ovulation. These six days are the ‘fertile window’ in a woman’s cycle, and reflect the lifespan of sperm (5 days) and the lifespan of the ovum (24 hours).

Ovulation is when a mature egg is released from the ovary, moves down the fallopian tube, and is available in the fallopian tube to be fertilised. If there is sperm waiting around at the time the egg is released, there is a higher chance that it will be fertilised. Ovulation happens about two weeks before the woman’s next expected period. So if her average menstrual cycle is 28 days, ovulation will happen around day 14.

If sex is timed five days before a woman’s ovulation, the probability of her getting pregnant is about 10%. The probability of pregnancy rises steadily until the two days before and including the day of ovulation. The likelihood of conceiving is dramatically increased if intercourse occurs in the three days leading up to and including ovulation.

At the end of a woman’s ‘fertile window’, the probability of pregnancy declines rapidly and by 12-24 hours after she ovulates, a woman is no longer able to get pregnant during that cycle.

Too complicated?

If your partner is not aware of her ‘fertile window’ or when she ovulates, she can find more information here. Otherwise, to cover all bases, sexual intercourse is recommended every 2 to 3 days to help optimise your chance of conceiving. But there’s no limit to how much sex you can have during that 6-day period.

The likelihood of actually becoming pregnant is dramatically increased if you have intercourse in the three days leading up to and including ovulation.

If sex is timed well on any of these three days, she has a 27-33% chance of becoming pregnant.

Adapted from data by Wilcox, A.J. et al. NEJM (1995) 333:1517

Myth conception

The myth:

"A woman can get pregnant any time of the month."

The truth:

The only time a woman can conceive is during the ‘fertile window’ of the menstrual cycle.

The ’fertile window’ in the menstrual cycle is the six days leading up to ovulation, when the egg is released from the ovary. This depends on how long the woman’s menstrual cycles are.

Not all women have the same length of cycle. If, on average, your partner has a period every 28 days the best chance of conceiving is between days 12 and 14 (with ovulation day on day 14). If she has a 24 -day cycle, then focus your efforts between days 7 and 10.

Fertile window calculator for different cycle lengths

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  • Fertile window
  • Most fertile time
  • Predicted ovulation day

Your fertile window is between days:

9 & 14

Your most fertile time is between days:

12 & 14

Your predicted ovulation day is:

Gauge your fertility potential Other factors affecting men's fertilityTiming - for women