Ovulation is the release of an egg, and it happens about 14 days before each period regardless of cycle length. That single fact makes it predictable — and it's the key to timing conception.
The constant luteal phase
The time from ovulation to the next period (the luteal phase) is remarkably consistent at about 14 days. Cycle length mostly varies in the days before ovulation. That's why ovulation = cycle length − 14.
The fertile window
An egg lives about 24 hours, but sperm can survive 3–5 days. So the fertile window begins several days before ovulation, and the best chance of conception comes from having intercourse in the lead-up to ovulation, not just on the day.
Why tracking beats guessing
Calendars assume regularity. Combining the estimate with physical signs or ovulation predictor kits catches the variation most cycles have, making the prediction genuinely useful.
Frequently asked questions
Around day 14 — ovulation usually happens 14 days before your next period, so the date moves with your cycle length.
Roughly 6 days: the 5 days before ovulation plus the day of ovulation itself, since sperm can survive for days inside the body.
Track your cycle length for a few months and use the average. If cycles are very irregular, consider ovulation kits or tracking signs rather than calendar prediction.