What is the Rule of Nines?

The Rule of Nines is a clinical tool that divides the adult body into regions each representing approximately 9% (or a multiple thereof) of total body surface area, allowing rapid TBSA burn estimation.

Does this work for children?

No. Children have different body proportions — their heads are relatively larger and legs smaller. The Lund and Browder chart is used for pediatric burn assessment instead.

What TBSA percentage is considered a major burn?

Generally, burns covering more than 25% TBSA in adults (or 20% in patients over 50 or under 10) are classified as major burns and require specialized burn center care.

Is this tool a replacement for professional medical assessment?

No. This tool is for educational and reference purposes only. Always seek immediate professional medical care for any significant burn injury.

Why does the perineum only count as 1%?

The perineum is a small anatomical region. Its 1% value accounts for the remaining surface area after all the major 9% regions are allocated, bringing the total to 100%.

How accurate is the Rule of Nines?

It provides a rapid and reasonably accurate estimate for clinical triage. For precise fluid resuscitation calculations, clinicians may refine the estimate using the Lund and Browder chart.

Burn Rule of Nines Calculator

Name: Burn Rule of Nines Calculator
Availability: InStock
Author: Nham Vu

Select burned body regions to instantly calculate the total body surface area (TBSA) percentage affected using the Rule of Nines.

Estimated TBSA Burned

of total body surface area

0%50%100%

Select regions to begin

Rule of Nines Reference

Region	TBSA
Head & Neck	9%
Anterior Trunk (chest)	9%
Anterior Trunk (abdomen)	9%
Posterior Trunk (upper)	9%
Posterior Trunk (lower)	9%
Each Arm	9%
Each Thigh	4.5%
Each Lower Leg & Foot	4.5%
Perineum	1%
Total	100%

Adult Burn Severity Guide

Minor — less than 10% TBSA. Outpatient treatment may be appropriate.

Moderate — 10%–25% TBSA. Hospital admission typically required.

Major / Critical — above 25% TBSA. Burn center referral strongly indicated.

This tool is for educational reference only. Always seek immediate professional medical care for burn injuries.

Summary

Select burned body regions to instantly calculate the total body surface area (TBSA) percentage affected using the Rule of Nines.

How it works

Click or tap a body region on the diagram or use the checkboxes to mark it as burned.
Each region contributes its fixed Rule of Nines percentage to the running total.
The TBSA percentage updates instantly as you select or deselect regions.
Review the severity classification (minor, moderate, major) shown alongside the TBSA.
Use the Reset button to clear all selections and start over.
Print or note the result to share with a medical professional.

Use cases

Emergency first-responder triage for adult burn victims.
Nursing and paramedic training on burn area estimation.
Medical student practice with the Rule of Nines algorithm.
Quick reference during burn unit patient intake.
Pre-hospital burn severity documentation.
Educational demonstrations in anatomy and trauma courses.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu