Figuring your Due Date

#1 - Count 40 weeks from beginning of last cycle #2 - Add 7 days to date of last period, count forward 9 months #3 - Ultrasound #4 - Use the form below to help you do the math

Method #1: Medical personnel may give you an estimated date of delivery. One way of estimating that date is counting 40 weeks from the first day of your last menstrual period. For example, say March 7th was the first day of your last menstrual period. Adding 40 weeks to this date would name December 11th as an estimated date of delivery. Method #2: A second way of calculating your due date is to add seven days to the first day of your last menstrual period and then add nine months to that day. For example, say March 7th was the first day of your last menstrual period. Adding seven days would bring that date to March 14th, then adding nine months would set December 14th as your estimated date of delivery.

Method #3: If your periods are irregular, neither of these systems may work for you. Doctors may choose to perform an ultrasound during your pregnancy in order to calculate the gestational age of your child. They will use this information to determine an estimated date of delivery Method #4: If you'd like to try this little program for figuring your due date, please fill in the information as requested. Please Note: This is not a medical test, but simply a mathematical calculation going through the same steps as are listed above. If you think you are pregnant, please contact your medical doctor, or feel free to contact us. The average duration of pregnancy is 280 days from the first day of the mother's last menstrual period. A normal full-term pregnancy can last anywhere from 38 to 42 weeks. 90% of babies are born within ten days before or after their due date. Remember that an estimated due date is only an educated estimate and a number of factors will determine the day you will deliver your child.

First Day of Last Menstrual Period:
(MM/DD/YYYY format)
(i.e. 08/05/2000)


Average Length of Cycles:
(22 to 45) Default: 28


Average Luteal Phase Length:
Ovulation (9-16) Default:14




Estimated Conception: 
Estimated Due Date:   
Estimated Fetal Age:  

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