Pregnancy & fertility · Free · Private
Ovulation calculator — fertile window for your next 3 cycles
Estimate your ovulation day, fertile window and next periods for the next three cycles from your last period date and cycle length.
How the estimate works
Ovulation usually happens around 14 days before your next period starts, not 14 days after the last one. So with a 28-day cycle it is around day 14, but with a 32-day cycle it is around day 18. The calculator applies this rule to your average cycle length.
Signs that can help
- Cervical mucus often becomes clear, slippery and stretchy near ovulation.
- Ovulation predictor kits detect the hormone surge that comes 24–36 hours before ovulation.
- Basal body temperature rises slightly after ovulation, which confirms it in hindsight.
When to see a fertility specialist
See a clinician if you have been trying to conceive for 12 months without success, or after 6 months if you are 35 or older. Seek advice sooner if your periods are very irregular or absent, or if you or your partner have a known condition that may affect fertility.
Get matched with a fertility clinic or read about fertility specialists.
Frequently asked questions
When is the fertile window?
Pregnancy is most likely from about five days before ovulation to one day after it, because sperm can survive for several days and an egg for about a day.
Can I use this calculator as contraception?
No. Calendar estimates are not reliable enough to prevent pregnancy. Talk to a clinician about effective contraception.
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