Pregnancy Due Date Calculator

Formula

LMP + 280 days

Worked example

LMP 2025-01-01 — 2025-10-08

Quick answer

What does the Pregnancy Due Date Calculator do?

Estimate a due date as 280 days after the first day of the last menstrual period.

What is the Pregnancy Due Date Calculator?

Estimate a due date as 280 days after the first day of the last menstrual period. Use it when you have the required inputs and want a deterministic, repeatable result with the calculation method visible.

How to use this calculator

Enter the values requested by the tool, keep units and time periods consistent, resolve any validation message, calculate, then review the primary answer together with the displayed formula and supporting values.

Formula and method

This calculator uses the deterministic formula LMP + 280 days. Enter the required values, then review the displayed substitution and result breakdown to verify the calculation.

Worked example

LMP 2025-01-01 2025-10-08

Common mistakes to avoid

Check units, decimal points, percentages, signs, date/time order, selector choices, and rounding. For important decisions, verify the result against an independent source or qualified professional when appropriate.