Burn Percentage Calculator

The Rule of Nines was published by Scottish surgeon A.B. Wallace in The Lancet in 1951 as a fast, memorable alternative to more detailed body-surface charts, and it remains the standard rapid-estimation method for total body surface area (TBSA) burned, dividing the adult body into regions that are each roughly 9% (or a multiple of 9%) of total surface area: head and neck 9%, each arm 9%, anterior and posterior trunk 18% each (split here into chest/abdomen and upper/lower back at 9% each), each leg 18%, and the genitalia/perineum 1%. A young infant's head is proportionally much larger and legs proportionally smaller, so this calculator adjusts those two regions for an infant under 1 year old: head rises to 18% and each leg drops to 13.5%, while the trunk and arm percentages stay the same. This infant adjustment is a single-step approximation, not the full age-graduated Lund-Browder chart clinicians use for children between roughly 1 and 9 years old, where head and leg percentages shift gradually with age rather than jumping at a single cutoff -- for a child older than 1 year, treat this calculator's TBSA as a rough adult-model estimate and use a Lund-Browder chart for a more accurate figure. Two of the individual body regions -- either leg alone -- are the single largest TBSA contributors in the adult model, each just under a fifth of the entire body surface (18%).

Once TBSA is totaled, the calculator applies the Parkland formula (4 mL of crystalloid per kilogram of body weight per percent TBSA burned) to estimate 24-hour fluid resuscitation volume, split evenly with half given in the first 8 hours from the time of burn (not from arrival) and the remaining half over the following 16 hours. The American Burn Association's consensus starting rate is actually somewhat lower than the classic 4 mL/kg/%TBSA Parkland figure -- roughly 2 mL/kg/%TBSA for adults and 3 mL/kg/%TBSA for children -- with the higher traditional Parkland volume now generally seen as an upper bound to titrate down from based on urine output; 4 mL/kg/%TBSA is what this calculator computes and is still a defensible, commonly taught starting point, but treat it as a ceiling rather than a fixed target. This total also does not include a patient's normal maintenance fluid requirement, which continues alongside burn resuscitation, particularly in children. Burns of 20% or greater TBSA (10% or greater in an infant) are classified as major and generally require formal fluid resuscitation; any genitalia/perineum involvement automatically triggers a burn center referral flag regardless of total TBSA, reflecting American Burn Association referral criteria that specific body regions and depths warrant specialist care independent of overall burn size.