Total Body Surface Area Burn Calculator

About this calculator

The rule of nines, introduced by surgeon Alexander Wallace in 1951, divides the adult body into regions that each represent roughly 9% (or a multiple of 9%) of total body surface area: the head and neck 9%, each arm 9%, the anterior and posterior trunk 18% each, each leg 18%, and the perineum 1%. It gives emergency physicians and paramedics a fast bedside estimate of how much skin surface a burn covers without needing a detailed body-surface chart, which matters because burn severity and fluid needs scale with the percentage of surface area affected, not the burn's absolute size.

That total body surface area percentage then feeds into the Parkland formula, developed at Parkland Memorial Hospital in Dallas by Dr. Charles Baxter in the 1960s, to estimate intravenous fluid resuscitation: 4 mL of crystalloid fluid per kilogram of body weight per percent TBSA burned over the first 24 hours, with half of that volume given in the first 8 hours from the time of injury. Burn units and trauma teams use this as a starting point for fluid resuscitation in adults with significant burns, adjusting the rate afterward based on urine output and other clinical signs.

This calculator estimates burned TBSA from the rule of nines and then applies the Parkland formula to that percentage and a given body weight to estimate initial 24-hour and first-8-hour fluid volumes.