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Ovulation Calculator
Estimate ovulation date and fertile window based on cycle length.
About This Calculator
Ovulation typically occurs 14 days before the next period — not 14 days after the last, as commonly misunderstood. The fertile window spans 5–6 days (sperm survive 3–5 days; egg is viable 12–24 hours). Cycle tracking apps like Clue and Flo use basal body temperature and LH surge data for more accuracy.