Pregnancy Due Date Calculator

Enter the first day of your last period — get the estimated due date, current week and trimester timeline.

Quick answer: Free pregnancy due date calculator: estimated due date from your last period, current week, trimester dates. Based on Naegele's rule.

First day of last period

Cycle length (days)

–Estimated due date

–Current week

–Trimester

–Conception ≈

Medical estimate only — always confirm with your healthcare provider.

How to use

Open this page on any device — no signup needed.
Fill in the fields above.
Get your result instantly — nothing is uploaded.

General information only — not medical, financial or legal advice. Figures cross-checked against public official sources (IRS / HMRC / NHS / WHO guidance); content last reviewed September 2026. For decisions that matter, confirm with a licensed professional in your country.

About this tool

The standard due-date estimate (Naegele's rule) adds 280 days to the first day of the last menstrual period, adjusted for cycle length. Only about 4% of babies arrive exactly on the due date — full term spans week 37 to 42. This tool also shows your current gestational week and trimester boundaries. It is an estimate, not medical advice.

FAQ

How accurate is the due date?

It is an estimate; most babies arrive between 37–42 weeks. Your doctor's ultrasound dating is the gold standard.

My cycle is longer than 28 days — does that matter?

Slightly — ovulation likely happened later. The calculator adjusts by your cycle length.

When does each trimester start?

First: week 1–13, second: week 14–27, third: week 28–birth.

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The complete pregnancy due date calculator guide

Prefer the long version — a worked example, the mistakes people actually make, and answers to real questions? The blog guide Pregnancy Due Date Calculator — Complete Guide, Mistakes & FAQ covers all of it step by step.

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Pregnancy Due Date Calculator

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The complete pregnancy due date calculator guide