Due Date Calculator
Enter the first day of your last period to estimate the due date, current pregnancy week and trimester.
Private by design: everything runs in your browser. Nothing is uploaded.
How it works
- Pick the first day of your last menstrual period.
- Hit Calculate — the due date is estimated with Naegele's rule (280 days).
- See your current week, trimester and how many days are left.
FAQ
What is Naegele's rule?
The standard estimate: add 280 days (40 weeks) to the first day of the last period. It assumes a typical 28-day cycle.
How are trimesters counted?
First trimester: weeks 1–13, second: weeks 14–27, third: week 28 until birth.
Is this medical advice?
No — it's an estimate only. Your doctor will confirm the due date, usually with an early ultrasound.