Baby Due Date Calculator
to Calculate Pregnancy Due Dates

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The online baby due date calculator on this page will instantly estimate the date your baby will be born on.

This free online pregnancy due date predictor will determine the due date and conception date based on the first day of your last menstrual period -- including what day of the week the due day falls on.

Plus, this due date estimator will also generate a list showing the dates of each of the 40-weeks of pregnancy, thereby also allowing you to calculate how many weeks pregnant you might be.

How to Calculate Due Date

The formula most often used to calculate a baby's due date is based on a calculation developed by a German obstetrician Dr. Franz Naegele back in the 1850s. Hence the formula is often referred to as Naegele's Rule.

Dr. Naegele's studies concluded that the average length of time between conception and a baby's birth was 266 days. His studies also showed that the average ovulation occurred 14 days days from the first day of a woman's last menstrual period. Therefore your baby's due date can be estimated by adding 280 days (14 + 266) from the first day of your last menstrual period.

Or, using a short-hand method, you can also estimate your baby's birth date by adding 7 days to the first day of your last period, and then subtracting 3 months from the result to get the month and day of the due date.

For example, if the first day of your last menstrual period was April 7th, your estimated due date would be January 14th (4/7 + 7 days = 4/14, minus 3 calendar months = 1/14).

With that I invite you to use the baby due date calculator to estimate the birth day of your baby and to generate dates for each of the 40-weeks following the first day of your last menstrual period.

Baby Due Date Calculator
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Instructions: Select the month, day, and year of the first day of your last menstrual period, and then click the "Calculate Baby Due Date" button.

Mouse over the blue question marks for a further explanation of each entry field. More in-depth explanations can be found in the glossary of terms located beneath the Baby Due Date Calculator.

Note that this pregnancy due date predictor generates due day and conception dates based on averages and therefore may not reflect your individual menstrual cycle and ovulation patterns.

Help First day of last menstrual period:
Help Estimated conception date:
Help Estimated delivery date:

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Baby Due Date Calculator Glossary of Terms

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First day of last menstrual period: Select the month, day, and year of the first day of your last menstrual period.

Estimated conception date: This is 14 days after the start of your last menstrual cycle as the baby due date calculator assumes you ovulated on Day 14 of your menstrual cycle (the average per Naegele's Rule).

Estimated delivery date: This is 280 days since the first day of your last menstrual period (ovulation on day 14 of cycle plus 266 days for average human gestation period).

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