Burn Area Calculator
Adult burn percent by rule of nines with severity bands.
What it does
Burn triage starts with area: the adult rule of nines splits the body into 9s and 18s plus 1% groin, counting second degree and deeper only. Thirty-six percent books a burn center; nine books urgent care.
The tool above takes each region extent with depth. It returns TBSA percent with a severity band.
The default front torso plus left arm plus half right leg totals 36%: major. A single full arm totals 9%: minor.
Regions follow American Burn Association guidance with Weber State teaching pages behind them. Both agree on 9/18 splits and first-degree exclusion used here.
How to use
- Set each body region extent.
- Pick burn depth.
- Read TBSA first.
- Read severity beside it.
- Cool with running water.
- Escalate per the band.
Formula
- region %
- Region percent of body surface.
- extent
- None, half, or full coverage.
- depth
- Second degree and deeper only.
Halves split regions evenly (half arm 4.5, half leg 9). Totals cap at 100 with 1% rounding. Depth select zeroes first-degree-only cases; palm estimates patchy burns outside this tool.
Worked example
Example: 36% TBSA
Defaults: front torso + left arm + half right leg, 2nd degree+.
- Front torso full: 18%.
- Left arm full: 9%.
- Right leg front half: 9%.
- Sum: 18 + 9 + 9 = 36%.
- Band: past 20 = major, burn center.
- First degree never counts in TBSA.
- Tool shows 36% TBSA, major burn center.
Reference table
| Region | Full | Half |
|---|---|---|
| Head and neck | 9% | 4.5% |
| Each arm | 9% | 4.5% |
| Chest / back | 18% each | 9% each |
| Each leg | 18% | 9% |
| Groin | 1% | n/a |
Limits
- Adults only; kids differ.
- Estimates, not medical advice.
- Depth needs clinical eyes.
- Inhalation injury sits outside.
Common mistakes
- Counting sunburn redness.
- Using adult nines on kids.
- Icing burns.
- Applying home creams deep.
- Delaying major-band transport.
Try it yourself
Quick checks. Answers sit tucked under each question.
Single full arm, 2nd degree?
One 9% arm: minor, urgent care.
Both legs full?
Two 18% legs: 36%, major burn center.
First degree only everywhere?
Full head plus arm at first degree: 0% counted.
Questions
What is the rule of nines?
Head 9, each arm 9, chest 18, back 18, each leg 18, groin 1. Front/back halves split evenly.
Do sunburns count?
No: red blanching first degree adds 0%. Count second degree and deeper only.
What do totals mean?
Under 10 minor, 10 to 20 serious ER, past 20 major burn center. Faces and hands upgrade care.
Do children use nines?
No: children run larger heads and smaller legs, so use Lund-Browder charts.
How are small burns sized?
Roughly 1%: the patient palm with fingers estimates scattered patches.
What is first aid?
Cool running water, no ice, loose cover, no home creams on deep burns, fast transport.