Due Date Calculator

Estimation of Due Date

The due date, also known as the estimated date of confinement, is an estimation of when a pregnant woman will deliver her baby. While the due date is often estimated as a single date, it can be helpful to consider a range of due dates, since only 4% of births occur on the estimated due date.

Last Menstrual Period

The default for this calculator bases the calculation on a woman's last menstrual period (LMP), under the assumption that childbirth on average occurs at a gestational age of 280 days, or 40 weeks. In terms of gestational age, pregnancies typically last between 37 and 42 weeks.

Ultrasound

Estimating due date based on ultrasound involves the use of soundwaves to look inside the body and compare the growth of the fetus to typical growth rates. It is a simple process that can be performed quickly and can be an accurate estimate of the due date early in the pregnancy.

Conception Date

Using conception date to estimate due date is similar to using the last menstrual period. There is a difference of about two weeks between using these two methods based on the timing between the last menstrual period and the date of conception.

In Vitro Fertilization (IVF)

When using in vitro fertilization, the estimation of the due date is generally more precise than calculating the due date based on natural conception, since the exact transfer date is known. The due date estimate is made based on the date of the 3-day or 5-day embryo transfer.