How to use the Due Date Calculator tool
3 simple steps · under a minute
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Choose your starting point
Use the first day of your last period, or a known conception date.
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Enter the date
Pick the date and, for your last period, your usual cycle length.
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See your due date
Read your estimated due date, how many weeks pregnant you are and key milestones.
About Pregnancy due date calculator
This pregnancy due date calculator estimates when your baby is likely to arrive. Doctors count a pregnancy as 40 weeks (280 days) from the first day of your last menstrual period, a method known as Naegele’s rule. If your cycle is longer or shorter than 28 days, the calculator adjusts the date accordingly.
If you know the date you conceived, choose “Conception date” instead — the due date is 266 days after conception. Your doctor or midwife may adjust your due date after an early ultrasound, which is the most accurate way to date a pregnancy.
Weeks pregnant today
Shows exactly how far along you are, and which trimester you are in.
Adjusts for your cycle
Longer or shorter cycles move the due date, just as doctors calculate it.
Milestone calendar
Dates for the end of each trimester, the anatomy scan, full term and more.
Frequently asked questions
How is a due date calculated?
Add 280 days (40 weeks) to the first day of your last period. For cycles longer or shorter than 28 days, add or subtract the difference.
How accurate is a due date?
It is an estimate. Only about 4–5% of babies are born on their due date; most arrive within two weeks either side.
Why does pregnancy count from the last period?
Because the exact day of conception is usually unknown, while the date of the last period is easy to remember. Ovulation normally happens about two weeks later.
When is the first trimester over?
The first trimester lasts until about the end of week 13. The second runs to the end of week 27, and the third until birth.
Is this medical advice?
No. Confirm your due date with your doctor or midwife.