Ovulation Calculator
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days
Estimate your ovulation date and fertile window based on your cycle length. Find your best days to conceive.
Enter your values below and click Calculate for instant results.
Ovulation is the release of a mature egg from one of the ovaries. It occurs approximately once per menstrual cycle and represents the only time during the cycle when pregnancy is possible. For a standard 28-day cycle, ovulation typically occurs around day 14, counting from the first day of the last menstrual period.
The fertile window extends beyond the day of ovulation itself. Sperm can survive in the reproductive tract for up to 5 days, while an egg is viable for only 12 to 24 hours after release. This means the most fertile days are typically the 5 days before ovulation and the day of ovulation itself.
The "14 days before the next period" rule applies across all cycle lengths. For a 28-day cycle, ovulation occurs around day 14. For a 35-day cycle, it occurs around day 21. The length of the follicular phase (from period to ovulation) varies between people and from cycle to cycle, but the luteal phase (from ovulation to next period) is relatively consistent at about 14 days.
Several physical signs can help confirm or predict ovulation. Basal body temperature rises slightly (0.2 to 0.5 degrees Fahrenheit) after ovulation and remains elevated until the next period. Cervical mucus changes from dry or sticky to clear and stretchy (often described as similar to raw egg whites) as ovulation approaches. Ovulation predictor kits detect the luteinizing hormone (LH) surge that occurs 24 to 36 hours before ovulation.
This calculator provides estimates based on average cycle patterns. Actual ovulation timing varies between individuals and from cycle to cycle. For fertility planning or contraception decisions, consult with a healthcare provider.