Curious when conception happened? Enter your due date or last period to find out.
Frequently Asked Questions
From a due date, we subtract 266 days (38 weeks). From your last menstrual period, we add the number of days until ovulation (typically cycle length minus 14). Both methods give an estimate since the exact moment of fertilization can't be known.
Not necessarily. Sperm can survive in the reproductive tract for up to 5 days. So intercourse that occurred up to 5 days before ovulation could have resulted in conception. The conception date refers to when fertilization most likely occurred, around ovulation.
The window accounts for the fact that sperm can survive 3-5 days in the reproductive tract and the egg remains viable for 12-24 hours. This means fertilization could have happened within a roughly 6-day window around ovulation.
An ultrasound can estimate gestational age based on the baby's size, which can be used to back-calculate an approximate conception date. First-trimester ultrasounds are most accurate for dating, typically within 5-7 days.
Gestational age (used by doctors) is counted from your last period, not from conception. So a pregnancy at 6 weeks gestational age is actually about 4 weeks since conception.