Total Body Surface Area Burn Calculator
Estimate burn surface area and starting fluids with the rule of nines.
Result
How it is calculated
Each of eight body regions is a Yes/No choice, and a Yes adds a fixed share of body surface: head and neck 9, each arm 9, front of the trunk 18, back of the trunk 18, each leg 18, genitalia 1. All eight add up to 100. The total is TBSA %. The fluid estimate is the Parkland formula 4 mL × weight (kg) × TBSA % for the first 24 hours, and the tool also shows half of it as the first-8-hour volume. Whole regions only: a region cannot be half burned, so a patchy burn must be rounded to Yes or No by the user. A value other than 0 or 1 in a region gives no result, and weight must be between 2 and 650 kg. With no region marked the tool shows 0 % and 0 mL. The shares are adult proportions.
Worked example
An 80 kg adult has burns on the right arm and the front of the trunk. Surface area: 9 + 18 = 27 %. Parkland volume over 24 hours: 4 × 80 × 27 = 8,640 mL. Half of this, 8,640 ÷ 2 = 4,320 mL, is the first-8-hour figure. The tool shows 27 %, 8,640 mL and 4,320 mL.
Common mistakes
- Marking a region Yes when only a small patch is burned. The tool counts the whole region, so one hand-sized burn on the leg becomes 18 % and the fluid figure jumps accordingly.
- Using the adult shares for a small child. The tool always uses the adult percentages, and head size, for example, differs in children.
- Reading the 8-hour figure as an extra amount. It is half of the 24-hour total, not in addition to it.
- Entering weight in pounds. 176 typed instead of 80 kg gives 19,008 mL instead of 8,640 mL, more than twice the fluid volume.
- Entering a weight outside 2–650 kg, or anything other than 0 or 1 for a region. The tool shows no result rather than guessing.
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% — with the perineum counted as the remaining 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.
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