Pregnancy Due Date Calculator
Estimate your due date from the first day of your last period (or your conception date), and see how far along you are.
Your result appears here.
By Shah Rukh, software developer · Last updated:
How the due date is calculated
Most due dates use Naegele’s rule: the first day of your last menstrual period (LMP) plus 280 days (40 weeks). If your cycle is longer or shorter than 28 days, the date is shifted by the difference. From a conception date, the due date is about 266 days later.
Trimesters
- First trimester: weeks 1–12
- Second trimester: weeks 13–26
- Third trimester: week 27 until birth
An early ultrasound often gives a more accurate date, and your midwife or doctor may update it.
This is an estimate for general information, not medical advice. Talk to a doctor or registered dietitian before making big changes.
Frequently asked questions
How accurate is a due date?
It’s an estimate. Only a small share of babies are born on their exact due date; most arrive within a couple of weeks either side.
Why count from my last period?
It’s easier to know than the conception date, so it became the standard starting point.
What if my cycles are irregular?
The estimate is less reliable. An ultrasound gives a better date.
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