How to Use This Pregnancy Conception Calculator
Select a calculation method, enter the required date, then click Calculate. The calculator will estimate the most probable conception dates and the possible range of dates when sexual intercourse may have led to the pregnancy.
Results are estimates based on averages for a single pregnancy.
About Conception
When Did I Conceive?
Many women ask this question when trying to figure out the exact day their pregnancy began. Often, gestational age is calculated from the first day of the mother's last menstrual period. Biologically, the baby was not conceived until ovulation and fertilization of the egg, which usually happens at least 10 days after the first day of the last menstrual period.
Last Menstrual Period
Conception usually occurs around 11–21 days after the first day of the last period of a woman who has a regular period. The estimation of conception date is based on this, but is rarely exact since it is difficult to know exactly when ovulation occurs.
Due Date
An estimated due date, usually based on a sonogram, is typically obtained from a healthcare provider during a prenatal visit. Based on this due date, a range of possible conception dates can be calculated.
Ultrasound
An ultrasound uses sound waves to create images of internal body structures. Ultrasounds can be used to measure a fetus as early as five or six weeks following the mother's last menstrual period. It is a more accurate measure in early pregnancy than in later stages.
Fertilization, Conception, and Pregnancy
Fertilization occurs when the sperm and egg combine in the fallopian tube, producing a fertilized egg. Conception refers to the process of becoming pregnant, which scientifically involves both fertilization and implantation into the wall of the uterus. A woman is considered pregnant when a fertilized egg has implanted into the wall of her uterus.
Related Calculators
Calculation Methods
Due Date
Enter your expected due date to estimate conception date.
Last Period
Enter the first day of your last menstrual period and average cycle length.
Ultrasound
Enter the ultrasound date and gestational age shown on the scan.
Track your pregnancy week by week with full milestone schedule.