Last menstrual period ultrasound dating
Once you have a general idea of when you ovulated, you can use an adjusted LMP to find your due date with a pregnancy wheel.
Ultrasound measurements for estimating the age of a fetus are more accurate during the early stages of pregnancy.
An ultrasound allows your doctor to measure the crown-rump length (CRL) — the length of the fetus from one end to the other.
During the first trimester, this measurement provides the most accurate estimation for the age of the baby.
The other way to calculate your due date is to use a pregnancy wheel. It’s very easy to estimate your due date if you have access to a pregnancy wheel.
The first step is locating the date of your LMP on the wheel.