Ovulation & Fertile Window Calculator

Find your most fertile days. Enter your last period date and cycle length to see your ovulation day, fertile window, and best time to try to conceive.

This calculator assumes a regular cycle with a 14-day luteal phase. Actual ovulation timing varies. For the most accurate tracking, consider using ovulation predictor kits (OPKs) or basal body temperature charting. Consult your healthcare provider for personalized fertility guidance.

How ovulation works

Ovulation occurs when a mature egg is released from the ovary, typically about 14 days before the start of your next period (the luteal phase). The egg travels down the fallopian tube where it can be fertilized by sperm for approximately 12–24 hours.

Since sperm can survive in the reproductive tract for up to 5 days, the "fertile window" is actually about 6 days long — the 5 days before ovulation plus the day of ovulation itself. Having intercourse in the 2–3 days before ovulation gives the highest chance of conception.

Reference: American College of Obstetricians and Gynecologists (ACOG) — Fertility Awareness-Based Methods of Family Planning.

This tool is for informational purposes only. It is not a substitute for medical advice or a reliable method of contraception. Consult your healthcare provider for personalized fertility guidance.