Estimate your ovulation date and fertile window from your last menstrual period and average cycle length.
Ovulation typically occurs about 14 days before the next period starts. The fertile window is the 5 days before ovulation plus the day of ovulation itself — sperm survive 3–5 days in the female reproductive tract; the egg is fertilisable for ~24 hours.
Cycles vary. This calculator assumes a regular cycle. If your cycle is irregular, ovulation predictor kits, basal body temperature tracking, or cervical-mucus monitoring are more reliable.
Estimates only. Fertility tracking is not a reliable form of contraception.
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