How long is the fertile window?
About six days. Sperm survive up to five days in the reproductive tract, but the egg is only viable for 12–24 hours, so the days before ovulation matter most.
Calculate your most fertile days and ovulation date based on your cycle length. Plan for conception with our free ovulation calendar.
Ovulation day = start of last period + (cycle length − 14). Fertile window = ovulation day − 5 to ovulation day + 1.
With a 30-day cycle starting 1 June, ovulation lands around 17 June and the fertile window is 12–18 June. Peak chance is the two days before ovulation.
About six days. Sperm survive up to five days in the reproductive tract, but the egg is only viable for 12–24 hours, so the days before ovulation matter most.
Rarely. The luteal phase is a stable 12–14 days for most people, which is why ovulation is counted backwards from the next period rather than forwards from the last one.
A sustained basal body temperature rise of 0.5°F, an LH surge on a urine test, or a shift to slippery egg-white cervical mucus all indicate ovulation occurred.