Retro Pregnancy Reverse Conception Birthday Calculator

    You know the birthday but when did conception happen?

    This retrospective retro pregnancy birthday conception calculator allows you to calculate the exact day of conception based on the weeks gestation and the delivery date. You can calculate this date more than 100 years in the past. Just enter the actual birthday of the baby and the weeks of pregnancy and we will automatically calculate the exact dates such as the range of dates when sex likely happened, when the baby was conceived, and the implantation date range,  


    How is the conception date calculated?

    Conception, the fertilization of the egg by the sperm usually happens 266 days before the due date and the due date is calculated 266 days after ovulation conception and fertilization. The last menstrual period is calculated to happen about 14 days before ovulation, so the due date is calculated 280 days after the first day of the last menstrual period.

    Did you ever wonder when the baby was conceived? Who the father is? 

    You can also try our scientifically-tested due date calculator.