# Due Date Calculator — How to calculate your due date

## How to calculate your due date

By Jillian Capewell |

# Due-Date Calculator

First day of your last period

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Cycle length

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The typical length of a pregnancy is 40 weeks, or 280 days, from the first day of your last normal menstrual period. If you know that date, then you’re set: just add nine months and seven days to it, and you’ve got a due date!

This is just an educated guess, however, based on the average 28-day length of a menstrual cycle. It’s estimated that less than 5% of pregnancies are delivered on their predicted due date, and if your cycle is typically longer or shorter than 28 days, this will affect your date.

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Jillian Capewell

Jillian Capewelll is an editorial assistant and graduate of SUNY Geneseo in upstate New York, where she was an editor for the college newspaper. Jillian started at Babble as an intern and returned after spending a year teaching Beatles songs to French children. She has wanted to write for a living since completing the construction-paper classic Penguin Surprise Do Stuff at age four with the help of her mom, who had to spell all the words. Aside from Babble, Jillian's work has also appeared on xoJane