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Simple Pregnancy Week Calculator — How It Works

Simple Pregnancy Week Calculator

Simple Pregnancy Week Calculator — How It Works

Estimates your current pregnancy week and due date from your last menstrual period.

How it works

  1. Enter the first day of your last menstrual period (LMP).
  2. The tool counts the days from that date to today and converts it into weeks and days of pregnancy.
  3. It also estimates your due date as 280 days (40 weeks) after your LMP, and tells you which trimester you’re in.

Formula

Gestational age = (Today − LMP date) in weeks and days
Estimated due date = LMP date + 280 days
Trimester: weeks 0–12 = 1st, weeks 13–26 = 2nd, weeks 27+ = 3rd

Example

If your last period started on March 1, 2026, by mid-June you’d be around 14 weeks, 5 days pregnant — in your second trimester — with an estimated due date in early December 2026.

Notes

This is a general estimate based on a standard 28-day cycle. Actual due dates vary, and an ultrasound dating scan from your healthcare provider is more accurate. This tool is not medical advice.

Try the Simple Pregnancy Week Calculator — instant results in your browser, no sign-up.

FAQ

Is this free?

Yes — the Simple Pregnancy Week Calculator runs entirely in your browser, no sign-up required.

Is this accurate?

The calculator performs the math precisely, but for dates that depend on local rules (holidays, time zone changes, medical estimates), treat the result as a planning guide rather than an official figure.