According to “rule of nines”, burns involving perineum are:

Burn Size (% BSA) Determination of burn size estimates the extent of injury. Burn size is assessed by Wallace rule of nines (By Alfred Russel Wallace) Wallace Rule of Nines: In adults: - Each upper extremity: 9% - Head and neck: 9% - Lower extremities: 18% - Anterior and posterior aspects of the trunk: 18%       - Perineum and genitalia: 1% Children have a relatively larger proportion of body surface area in their head and neck, which is compensated by a relatively smaller surface area in the lower extremities.  - In infants: Head and neck- 21%; Each leg-13% Berkow formula is used to accurately determine burn size in children. For estimating smaller burns: Area of open hand (including palm and extended fingers) of the patient is approximately 1% of TBSA. This method is helpful in evaluating splash burns and burns of mixed distribution.