How the Rule of 9s works
The Rule of 9s divides the body into regions worth ~9% (or multiples) of total body surface area (TBSA). It’s a fast field estimate—confirm with your protocols when possible.
| Region | Adult % | Pediatric % (approx.) |
|---|---|---|
| Head & Neck | 9 | 18 |
| Anterior Trunk | 18 | 18 |
| Posterior Trunk | 18 | 18 |
| Each Arm | 9 | 9 |
| Each Leg | 18 | 13.5 |
| Perineum | 1 | 1 |
Pediatric values vary with age—pair with structured pediatric assessment using PAT & ABCDE.
- Airway involvement: facial burns, soot, singed hairs, hoarseness
- >10% TBSA partial/full thickness in children; >15% in adults
- Circumferential limb or chest burns; chemical/electrical burns
- Associated trauma or altered mental status
Escalate per protocols and coordinate via Contact Us if needed.
Quick TBSA Calculator (Rule of 9s)
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Bottom line
Use the Rule of 9s for a rapid TBSA estimate, watch for airway or high-TBSA red flags, and manage fluids per protocols. For children, combine with the structured PAT & ABCDE approach.
Educational only; not medical advice.