Knowing when you ovulate is one of the most useful pieces of information when you’re trying for a baby. Most women ovulate roughly halfway through their menstrual cycle, and there are around six days each month when conception is most likely — the five days leading up to ovulation and the day itself.
Use the calculator below to estimate your fertile window based on the first day of your last period and the usual length of your cycle.
Enter the first day of your last period and your average cycle length to estimate your ovulation day, fertile window, and next period.
This is an estimate based on calendar averages and is not a substitute for medical advice or a reliable form of contraception.
Ovulation is the release of a mature egg from one of your ovaries. Once released, the egg travels down the fallopian tube, where it can be fertilised by sperm for around 12 to 24 hours. Sperm, on the other hand, can survive inside the body for up to five days — which is why the days leading up to ovulation are just as important as the day itself.
In a typical 28-day cycle, ovulation tends to happen around day 14, but every woman is different. If your cycle is shorter or longer, ovulation shifts accordingly.
Alongside the calendar, your body often gives subtle clues that ovulation is approaching:
Tracking these signs alongside the calculator gives you a fuller picture than dates alone.
It gives a good estimate for women with reasonably regular cycles, but it can’t predict ovulation precisely. If your cycle is irregular, consider using it alongside ovulation predictor kits or cervical mucus tracking.
Aim for the five days leading up to ovulation and the day of ovulation itself. Having sex every two to three days throughout the cycle is another simple approach that doesn’t require tracking at all.
Around 8 in 10 couples will conceive within a year of trying. If you’re under 35 and haven’t conceived after a year of regular unprotected sex, or under 40 and haven’t conceived after six months, it’s worth speaking to your GP.
Yes, ovulation can happen before periods return — for example, after stopping contraception or while breastfeeding. That’s why it’s possible to become pregnant before your first period back.
Yes. Significant stress, sudden weight change, intense exercise and illness can all delay or skip ovulation in a given month.
