Ovulation Calculator

Ovulation typically occurs 14 days before the start of your next period. For a standard 28-day cycle, that means day 14. For longer or shorter cycles, subtract 14 from your cycle length to find your estimated ovulation day. For example, a 32-day cycle means ovulation around day 18. This calculator does that math automatically based on your last period and cycle length.

The fertile window is the roughly 6-day period when pregnancy is possible — the 5 days before ovulation and ovulation day itself. Sperm can survive in the reproductive tract for up to 5 days, so having intercourse in the days leading up to ovulation (not just on ovulation day) significantly increases chances of conception. The egg survives only 12–24 hours after ovulation.

Common ovulation signs include: a rise in basal body temperature (BBT) of 0.2–0.5°F after ovulation; cervical mucus that becomes clear, stretchy, and egg-white-like; a positive ovulation predictor kit (OPK) result; mild one-sided pelvic cramping (mittelschmerz); and breast tenderness. BBT charts and OPKs together are the most reliable at-home tracking methods.

For couples under 35 with no known fertility issues, about 85% conceive within 12 months of trying. Around 30% conceive in the first cycle, 75% within 6 months, and 90% within 12 months. If you're under 35 and haven't conceived after 12 months of timed intercourse, or over 35 after 6 months, speaking with a reproductive endocrinologist is recommended.

It's extremely unlikely but not impossible due to cycle variability. Ovulation can shift with stress, illness, travel, or changes in sleep. If your cycles are irregular, your fertile window can be harder to predict. Tracking multiple cycles and using additional methods like OPKs or BBT charting gives you a more accurate picture than relying on a single calculation.