All Tools

Pregnancy Due Date Calculator

Find your estimated due date, current week, and trimester

Enter Your Details

Your Pregnancy Details

Estimated Due Date
—
—
Current Week—
Trimester—
Days Remaining—
Days Pregnant—
Conception Estimate—

Development Milestones

Related Tools

Age Calculator Calorie Calculator BMI Calculator Date Difference

How Due Date Calculation Works

This calculator uses Naegele's Rule, which estimates the due date by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). If you know your conception date, we add 266 days (38 weeks) instead.

Only about 5% of babies are born on their exact due date. Most arrive within a 2-week window around the estimated date. Your healthcare provider may adjust the due date based on ultrasound measurements.

Frequently Asked Questions

How is the due date calculated?
The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is called Naegele's rule. If using conception date, 266 days (38 weeks) are added.
How accurate is a due date calculator?
Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after. Early ultrasound dating (before 12 weeks) is the most accurate method.
What are the three trimesters?
First trimester: weeks 1-12 (organs form), Second trimester: weeks 13-26 (rapid growth, movement felt), Third trimester: weeks 27-40 (brain development, weight gain, preparation for birth).

Go deeper

Read the SnoopTool guide behind this tool

The calculator gives you the number. These SnoopTool guides explain the method, the assumptions and the decision — with worked examples, data tables and FAQs.

Browse all SnoopTool guides →

Answers, not just a number

Short, exact answers to the questions people ask alongside this tool — the number first, then the working.

For teams, not just visitors

Want this calculator on your own site?

We build the calculators on SnoopTool as embeddable widgets in your branding, wired to your own lead form — the same maths, your colours, your domain, your leads. Tell us which one and we will send back a working demo you can put in front of your team.

One reply from a person, within one business day. No newsletter, no sequence. See our privacy policy.