On This Page ► Due dates can be calculated either by formula or from ultrasound measurements of the growing baby.
Formulas are quick and easy and can be used by anyone.
A due date calculator calculates your estimated due date (EDD) which is an ESTIMATE of the day you are likely to go into labor spontaneously (without medical intervention).
Only about 4% of babies are born on their estimated due dates but the majority (70%) are born within 10 days either side of their due dates.
The Estimated Due Date (EDD) is an important date for pregnant women and their health care providers as it sets benchmarks for the pregnancy as well as an estimate of when baby is due.
The estimated due date is also known as the estimated date of confinement (EDC).
It is also the appropriate method for calculating due dates when pregnancies result from artificial reproductive techniques (ART).
Read more The terminology of pregnancy dating is based on the LMP formula.
Counting pregnancy from LMP is the basis of gestational ageing which is the way pregnancy progress is measured and recorded.
Since the actual date of conception is not normally known, the LMP formula begins counting pregnancy from the first day of a women's last menstrual period (LMP).
This can be a little confusing since counting starts about two weeks before true pregnancy begins.