Calculating Your Due Date
If you have regular 28 day cycles, figuring out your estimated due date is simple. Add 7 days to the first day of your last normal menstrual period. Then count backwards 3 months. That's it!
Here's an example - let's say your last menstrual period started on June 14. Add 7 days to June 14 and it equals June 21. Then count backwards 3 months and March 21 becomes your estimated due date.
Or, use our calculator below. Fill in the fields in the top 2 rows, hit "Calculate!" and the information in the bottom 3 rows will be automatically generated.
When you start prenatal care, your doctor or midwife may check an ultrasound to confirm your due date. If you're not sure when your last period started, or if your periods are irregular, the ultrasound may change your due date.
Reviewed By: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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