Burn Percentage Calculator (%TBSA From Burned Area)

Calculate burn percentage (%TBSA) from burned area and total body surface area in m², ft² or cm², or solve for the burned area or total area.

Safety notice: This calculator is for educational use only and does not diagnose burn severity or replace medical evaluation. Seek urgent/emergency care for trouble breathing, suspected inhalation injury, electrical/chemical burns, deep/white/charred burns, burns to the face/hands/feet/genitals/major joints, large or worsening burns, severe pain, fever, or signs of infection (especially in infants or older adults). For professional guidance, consult resources such as the American Burn Association burn-center referral criteria.

Burn Percentage Formula

The burn percentage is the burned area expressed as a percentage of total body surface area, often written as %TBSA. Select the value to solve for, enter the two known values, and select Calculate. For clinical %TBSA, include partial- and full-thickness burns and exclude superficial burns, consistent with the American Burn Association guidance. The tool does not identify burn depth.

Burn Percentage = (Burned Area / TBSA) \times 100

Burned Area = TBSA \times (Burn Percentage / 100)

TBSA = Burned Area / (Burn Percentage / 100)

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 = 0.09290304 m²	10 ft² = 0.9290304 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. Children and infants require adjusted body proportions, such as a Lund–Browder assessment. The table is a clinical reference, not a feature of this calculator.

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.

Burn Percentage = (0.36 / 1.8) \times 100 = 20%

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%.

Burned Area = 2.0 \times (15 / 100) = 0.30 m²

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.