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Pregnancy Due Date Calculator

Track key pregnancy milestones, your current week and trimester, and your estimated due date from your last menstrual period.

Enter your last period date to see results.

🔒 100% private — calculations run in your browser. Nothing is uploaded.

About the Pregnancy Due Date Calculator

Pregnancy is usually dated from the first day of your last menstrual period (LMP) and lasts about 40 weeks, split into three trimesters. Knowing your current week and trimester helps you follow your baby's development and prepare for appointments and milestones.

This calculator estimates your due date using Naegele's rule — adding 280 days to the first day of your last period — and tells you which week and trimester you're currently in. Due dates are estimates: only about 1 in 20 babies arrive exactly on the predicted day, and an ultrasound dating scan gives a more precise figure.

Frequently asked questions

How is my due date calculated?⌄

The common method (Naegele's rule) adds 280 days, or 40 weeks, to the first day of your last menstrual period. This calculator does that automatically and also shows your current week.

Why is pregnancy counted from my last period?⌄

Because the exact date of conception is usually unknown, doctors date pregnancy from the first day of the last period, which is easier to pinpoint. This means the first two weeks are counted before conception actually occurs.

How accurate is the due date?⌄

It's an estimate. Most babies arrive within a week or two either side of the due date. An early ultrasound can refine the date, especially if your cycles are irregular.

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