Conception Date Calculator

Conception occurs when a sperm fertilises an egg. Since ovulation typically happens around day 14 of a 28-day cycle (14 days before the next period), conception date is estimated as LMP + (cycle length - 14) days. Working backwards from a due date: conception = EDD - 266 days (38 weeks).

The exact date of conception is usually unknown because sperm can survive in the reproductive tract for up to 5 days, and ovulation is not always detected. The LMP is a well-known, consistent starting point. Standard medical practice adds 2 weeks to embryonic age to get gestational age.

Rarely. Even with careful cycle tracking, ovulation prediction kits, or basal body temperature monitoring, conception can occur up to 5 days after intercourse (due to sperm survival). First-trimester ultrasound dating provides an accurate EDD, but the conception window still spans several days.

The estimated conception window typically spans 3-6 days around the estimated ovulation date. A first-trimester ultrasound (7-13 weeks) can date the pregnancy to within 5-7 days. Second-trimester ultrasound is less accurate. For medicolegal purposes, no calculator can determine paternity; DNA testing is required.

The fertile window is the 6-day period ending on ovulation day: the 5 days before ovulation plus ovulation day itself. Sperm can survive up to 5 days in the female reproductive tract, and an egg is only viable for 12-24 hours after ovulation. Conception is most likely from intercourse on the 1-2 days before or on ovulation day.