Pregnancy Due Date Calculator

Calculate your estimated due date from your last menstrual period. Free online pregnancy calculator with trimester timeline.

Select the first day of your last menstrual period

Select the first day of your last menstrual period

How It Works

  1. Enter the first day of your last menstrual period (LMP).
  2. Optionally adjust your average cycle length for a more accurate estimate.
  3. The calculator applies Naegele's rule: LMP + 280 days.
  4. Your estimated due date (EDD) and current gestational week are displayed.
  5. Note: only about 4% of babies arrive exactly on the due date - it is a statistical estimate.

Formula

EDD = LMP + 280 days (Naegele's rule, assumes 28-day cycle)
Gestational age = Today - LMP (in weeks and days)

Example

Input: Last menstrual period: January 1
Result: Estimated due date: October 8 Gestational week: calculated from today

FAQ

It is the standard formula for estimating the due date: add 280 days (40 weeks) to the first day of the last menstrual period.

Most babies arrive within 2 weeks of the EDD. Only about 4% are born exactly on the estimated date.

No. All calculations run entirely in your browser. No personal data is ever sent to a server.

An early ultrasound (8-12 weeks) is the most accurate way to confirm gestational age and estimated due date.