Calculate burn percentage (%TBSA), burned area, or TBSA from known area values in m², ft², or cm². This tool does not estimate burned area from body regions or replace Rule of Nines or Lund–Browder assessment.
Burn Percentage Formula
The burn percentage is the burned area expressed as a percentage of total body surface area, often written as %TBSA. The calculator can solve for burn percentage, burned area, or total body surface area when you enter any two of the three values.
- Burn Percentage is the percent of total body surface area affected by the burn.
- Burned Area is the measured or estimated surface area affected by the burn.
- TBSA is total body surface area.
If you enter TBSA and burned area, the calculator finds burn percentage. If you enter TBSA and burn percentage, it finds burned area. If you enter burned area and burn percentage, it finds the total body surface area implied by those values. Area values are converted internally to square meters before the formula is applied, then converted back to the selected unit when needed.
Area Unit Conversions Used
The calculator uses square meters as the base area unit.
| Unit | Conversion to m² | Example |
|---|---|---|
| m² | 1 m² = 1 m² | 1.80 m² stays 1.80 m² |
| ft² | 1 ft² = 0.092903 m² | 10 ft² = 0.92903 m² |
| cm² | 1 cm² = 0.0001 m² | 500 cm² = 0.05 m² |
Common Adult Rule of Nines Estimates
When exact burned area is not measured, clinicians often estimate %TBSA using body regions. The adult rule of nines is a quick estimate and is not the same as measuring the area directly.
| Adult body region | Approximate %TBSA |
|---|---|
| Head and neck | 9% |
| Each arm | 9% each |
| Anterior trunk | 18% |
| Posterior trunk | 18% |
| Each leg | 18% each |
| Perineum | 1% |
Examples
Example 1: Calculate burn percentage
You have a TBSA of 1.8 m² and a burned area of 0.36 m².
The burn percentage is 20% TBSA.
Example 2: Calculate burned area
You have a TBSA of 2.0 m² and a burn percentage of 15%.
The burned area is 0.30 m².
FAQ
What does %TBSA mean?
%TBSA means percent of total body surface area. A burn percentage of 10% means the burned area is estimated to cover 10% of the person’s total skin surface area.
Can burned area be greater than TBSA?
No. Burned area cannot be greater than total body surface area. If burned area is larger than TBSA, the result would be more than 100%, which is not valid for this calculation.
Is this the same as a medical burn assessment?
No. This calculator only performs the area percentage math. Burn severity also depends on depth, location, age, inhalation injury, other injuries, and medical history. For a real burn injury, use clinical assessment and emergency care guidance rather than relying only on the percentage calculation.
