Calculate expected delivery date and key pregnancy milestones with standard dating methods.
Overview
Due date calculators estimate expected date of delivery (EDD) using obstetric dating rules, most commonly from the first day of the last menstrual period (LMP).
Actual delivery can vary by weeks, so EDD is best understood as a planning anchor rather than an exact prediction.
Steps
Use LMP, conception date, or IVF transfer date.
Input exact date based on selected method.
Adjust if cycle differs from 28 days.
Apply standard gestational timing model.
See trimester windows and likely viability checkpoints.
First-trimester scan refines clinical dating.
Math
EDD (LMP method) = LMP + 280 days; Conception date = EDD - 266 days
Gestational age is counted from LMP, so a full-term estimate uses 40 weeks (280 days) from that date.
Worked cases
EDD = March 1 + 280 days
Estimated due date: December 6, 2026
EDD = conception + 266 days
Estimated due date: January 1, 2027
EDD = transfer date + 261 days
Estimated due date: February 5, 2027
Why use this
Questions