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Find your fertile window and ovulation day based on your cycle length.
Ovulation Calculator estimates your next ovulation day and 6-day fertile window from your last period and cycle length, and projects the fertile windows for the next 3 cycles.
Calculate your ovulation day and 6-day fertile window based on your last period and cycle length. See the best days to conceive and plan ahead with 3-cycle projections.
Enter the first day of your last menstrual period
Confirm your average cycle length (default 28 days)
See your ovulation day, fertile window, and next period date
View 3-cycle projection to plan ahead
Ovulation is estimated to occur 14 days before the next period: ovulation date = LMP + cycleLength − 14. The fertile window spans ovulation − 5 days to ovulation + 1 day (6 days total). Projections for subsequent cycles repeat the same interval. This is an estimate based on cycle regularity; use clinical ovulation testing for confirmed timing.
Ovulation typically occurs 14 days before your next period, not 14 days after your period starts. For a 28-day cycle, that's Day 14. For a 32-day cycle, it's around Day 18.
The fertile window spans approximately 6 days: the 5 days before ovulation plus the day of ovulation. Sperm can survive up to 5 days in the reproductive tract, so intercourse before ovulation can still result in conception.
The 2–3 days before ovulation and the day of ovulation are when pregnancy is most likely. An egg survives only 12–24 hours after release, so timing intercourse around ovulation is key.
This calculator assumes a regular cycle length. For irregular cycles (varying by more than 7 days), ovulation timing is less predictable — consider ovulation predictor kits (OPKs) or basal body temperature (BBT) tracking for better accuracy.