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Calculating Your Due Date:

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 three 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 by a few days.

Calculator-2: Due Date Calculator:

Last Menstrual Period:

(MM/DD/YYYY)

Average Length of Cycles:

(22 to 45)
(defaults to 28)


Estimated Conception:
Estimated Due Date:
Week of Pregnancy:
  • Reviewed last on: 10/22/2008
  • Peter J. Chen, MD, Department of Obstetrics & Gynecology, Hospital of the University of Pennsylvania, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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