Health · Pregnancy

Pregnancy due date calculator

Estimate your due date and how far along you are, based on your last period or your conception date.

Mode

Most calculators assume 28 days. Adjust if yours runs longer or shorter.
Estimated due date
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Today, you're—
Trimester—
Days until due date—

Rough sheet

step-by-step
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How the due date is estimated

Using Naegele's rule, the standard method behind this calculator, a due date is estimated as 280 days (40 weeks) after the first day of your last menstrual period, based on an assumed 28-day cycle. If you enter a conception date instead, it adds 266 days — the average length of pregnancy counted from conception rather than from the last period — which lands on roughly the same estimated date for a typical cycle.

Frequently asked questions

It's an estimate. Only a small share of babies arrive on their exact due date, and a full-term pregnancy is generally considered anywhere from 37 to 42 weeks. Your care provider may adjust the date after an ultrasound.

Switch to conception-date mode, which adds 266 days to the conception date instead of 280 days to the last period — both land on roughly the same due date for a 28-day cycle.