Ovulation & Period Calculator (2026)

Ovulation typically happens about 14 days before your next period starts, because the luteal phase (after ovulation) is fairly constant at around 14 days. So for a 28-day cycle you ovulate around day 14; for a 32-day cycle, around day 18. This calculator works out the date from your cycle length.

The fertile window is roughly the five days before ovulation plus ovulation day itself — about six days in total. Sperm can survive up to five days in the reproductive tract, while the egg lives about 24 hours, so intercourse in the days leading up to ovulation gives the best chance of conception.

It is an estimate based on a regular cycle. Real ovulation shifts from cycle to cycle, and stress, illness, or irregular cycles change the timing. For more precision, combine the calendar estimate with ovulation predictor kits (LH tests) or basal body temperature tracking.

No. Calendar-based estimates are not reliable contraception because ovulation timing varies. If you are trying to avoid pregnancy, use a proven contraceptive method and speak to a doctor or a clinic. This tool is for family planning and general awareness only, not medical advice.