According to the Rule of Nines for adults, what percentage of body surface area is the head and neck combined?

• A. 18%
• B. 4.5%
• C. 9%
• D. 13%

Answer: (C)

Understanding how the Rule of Nines estimates burn size in adults helps you quickly gauge fluid needs. For adults, the head and neck together make up about 9% of total body surface area. This single figure comes from combining two regions (head and neck) that together sum to 9%. In the same rule, the arms are 9% each, the trunk is 18% (front) plus 18% (back), each leg is 18%, and the perineum is 1%. So the head and neck combined being 9% fits consistently with the standard distribution. The other numbers correspond to different regions (for example, 4.5% is half of the head or half of the neck individually), which is why they don’t represent the combined head and neck area.