Summary
Cycle-adjusted due-date estimate from LMP — confirm with clinical dating.
Calculation details
The cycle-adjusted Naegele method uses calendar-safe UTC dates. Dating by a clinician or ultrasound may differ.
Formula
Due date = LMP + 280 days + (cycle length - 28 days).
Worked example
Pregnancy due date worked example
A 28-day cycle gives an estimated due date 280 days after LMP.
How it works
Enter the first day of the last menstrual period and usual cycle length. Confirm dating with clinical care; ultrasound timing can differ.
Frequently asked questions
Is this a medical diagnosis?
No. It is an educational estimate and cannot diagnose a condition or replace individualized professional advice.
Why can my actual result differ?
Cycle irregularity and clinical dating (including ultrasound) often differ from LMP math.
When is this calculator most useful?
Use it for an educational LMP-based estimate only — confirm dating with prenatal care.
How are results rounded?
The calculation retains full precision; centralized display formatting rounds only the visible result.