How ovulation timing works
Ovulation usually happens 14 days before your next period — not 14 days after your last one. So the formula is: ovulation = next period date − luteal phase length. The fertile window is about 6 days: the 5 days before ovulation (sperm can survive up to 5 days) plus ovulation day itself (egg lives ~24h).
Important caveats
- Cycles vary — only ~30% of women have a textbook 28-day cycle; ovulation can shift from month to month.
- This is a prediction, not a test — the most reliable way to confirm ovulation is tracking basal body temperature, cervical mucus, or using OPK (ovulation predictor kit) tests.
- The luteal phase is usually consistent (12–16 days) for an individual, but the follicular phase varies — that's why cycle length drives the math.
- Irregular cycles? Track for a few months first — the calculator needs a typical length to be meaningful.
Informational use only; not a contraceptive method and not medical advice.