Ovulation Calculator

How it works

Ovulation typically occurs 14 days before the next expected period: ovulation day = LMP + (cycle length − 14). Fertile window spans 5 days before ovulation through 1 day after (sperm can survive 3–5 days; egg lives 12–24 hours). Cycle length varies by 2–3 days month-to-month for most women. Basal body temperature (BBT) charting and LH ovulation tests provide more accurate timing than calendar methods.