Calculate your next ovulation date, fertile window and next period based on your cycle.
Ovulation timing is one of the most practical things to understand when you're trying to conceive. The fertile window — the days when pregnancy is possible — is typically only about 6 days per cycle: the 5 days before ovulation and the day of ovulation itself. Knowing when that window falls makes a real practical difference.
This calculator estimates your ovulation date and fertile window based on the first day of your last period and your average cycle length. It's a probability-based estimate, not a certainty — ovulation timing can shift with stress, illness, travel, and other factors.
If you've been trying to conceive for 12 months (or 6 months if you're over 35) without success, it's worth speaking to your GP about further investigation rather than continuing to rely solely on timing.
Common signs include a change in cervical mucus (becoming clearer and more stretchy, like egg white), a slight increase in basal body temperature after ovulation, and sometimes mild one-sided pelvic pain (mittelschmerz). OTC ovulation predictor kits detect the LH surge that precedes ovulation and are widely used.
Irregular cycles make calendar-based prediction less reliable. Tracking basal body temperature, using OPK tests, and monitoring cervical mucus give more direct signals of ovulation regardless of cycle length.
Sperm can survive in the female reproductive tract for up to 5 days under the right conditions. This is why the fertile window extends 5 days before ovulation — having intercourse in the days leading up to ovulation can still result in conception.
If you're under 35 and have been trying for 12 months without success, or over 35 and tried for 6 months, see your GP. Earlier if you have known conditions like PCOS, endometriosis, irregular periods, or a history of pelvic infections.