In the adult Rule of Nines, what percentage is attributed to one arm (including both anterior and posterior surfaces)?

• A. 4.5%
• B. 7%
• C. 9%
• D. 18%

Answer: (C)

Estimating burn size quickly relies on the Rule of Nines, which assigns percentages to large body regions to approximate total body surface area. An arm, counting both anterior and posterior surfaces, accounts for nine percent because each surface is 4.5% (front 4.5% plus back 4.5%), totaling 9% for the entire arm. This quick breakdown helps guide fluid resuscitation and initial management. For reference, the head is 9%, each leg is 18%, the trunk is 18% anterior and 18% posterior (together 36%), and the perineum is 1%. In children, proportions differ, so pediatric methods like Lund and Brower are used for more accuracy.