Due Date Calculator
Estimate your due date and how far along you are from the first day of your last menstrual period and your usual cycle length.
Result
How it is calculated
The calculator uses Naegele’s rule: the estimated due date is 280 days (40 weeks) after the first day of your last period, assuming a 28-day cycle. If your cycle is longer or shorter, the date shifts by the difference. Weeks of pregnancy are also counted from your last period, even though conception usually happens about two weeks later.
An estimate, not an exact date
Only a small share of babies arrive on their due date; most are born between 37 and 42 weeks. A first-trimester ultrasound gives a more precise estimate, and your doctor or midwife will usually go by that.
Related guide: How Far Along Am I? How Pregnancy Weeks and Due Dates Are Calculated
Frequently asked questions
When does each trimester start?
The first trimester runs through the end of week 13, the second from week 14 to week 27, and the third from week 28 until birth.
What if I do not remember my last period?
Use your best estimate and confirm with an ultrasound. Measuring the embryo in the first trimester is the most reliable way to date a pregnancy.
Is my information stored?
No. The calculation runs in your browser and nothing is sent to a server.
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Results are estimates for informational purposes only and are not financial, tax, legal or medical advice.