Trying to estimate when your baby will be born can be a complex task. You can find calculators that will tell you, your doctor will offer a guess and your first ultrasound will shed some light on when the big day may be. Chances are you will also try to figure out the due date on your own. You can narrow it down by performing calculations in different ways, but no method is 100 percent accurate. The American Pregnancy Association notes that less than 5 percent of babies are actually born on their due date.
Step 1
Add seven days to the first day of your last period and subtract three months to calculate your due date, according to BabyHopes.com.
Step 2
Calculate the first day of your last period and, using a calendar, subtract 281 days for the estimated due date.
Step 3
Add 267 days or 38 weeks, the length of a typical pregnancy, to the date of conception if you are certain when it happened.
Tips and Warnings
- Most pregnancy due date calculations are based on a 28-day menstrual cycle. Add or subtract numbers accordingly if yours is usually longer or shorter.
