Estimating TBSA burned is critical to the initial management and fluid resuscitation of patients who have sustained burn injuries. TBSA of scattered burn injuries are frequently estimated using the patient's percentage palmar surface area (%PSA), which is taught as being 1% of the TBSA. This study investigates the relationship of %PSA to TBSA as the body mass index (BMI) increases. Age, sex, race, weight, height, and PSA was collected from obese and nonobese volunteers. TBSA was calculated using the Mosteller, DuBois-DuBois, Livingston and Scott, and Yu formulas. The %PSA relative to TBSA was calculated in obese and nonobese volunteers. Data from 100 subjects were collected. Fifty subjects had a BMI >30 and 50 had a BMI <30. The average age was 41 years (22-77 years old). There were 68 women and 32 men. The %PSA ranged from 0.49% of TBSA with a BMI of 58.7 to 1.15% of TBSA with a BMI of 22.6. This correlation of %PSA to BMI was statistically significant with all of the formulas. We should not assume that the %PSA is always 1% of TBSA, especially in obese patients.