In the Rule of Nines for adults, what percentage is assigned to the genitalia?

• A. 9%
• B. 1%
• C. 18%
• D. 13.5%

Answer: (B)

Estimating burn size in adults uses the Rule of Nines, which assigns specific percentages to large body regions. The genital area is a small region called the perineum and is allocated 1% of the total body surface area. So, in the overall TBSA calculation, the genitalia contribute 1%, while the other regions—such as the head (9%), each arm (9%), the front and back of the trunk (18% each), and each leg (18%)—account for the rest. That makes 1% the correct figure for the genital area. The other percentages correspond to larger regions, not the genitalia (for example, 9% covers the head or an entire arm, 18% covers the trunk or a leg, and 13.5% isn’t used in this rule).