Health calculators

TBSA Calculator

Updated Sep 5, 2026 By Jehan Wadia
Rate Formulas Medical disclaimer
Body Regions — Rule of Nines
Body Map (updates as you select)
Front View
Back View
Not burned Burned — depth not set Superficial (1st°) Partial (2nd°) Full thickness (3rd°)
TBSA Results
Total TBSA Burned
31.5%
Unburned body surface: 68.5%
Critical TBSA (Partial + Full Thickness)
22.5%
Excluded: 9% superficial / unclassified
Major / Serious Burn — 20%–39%
Requires referral to a specialized burn center.
Per-Region Breakdown
    Superficial (first-degree) burns are not typically included in clinical TBSA calculations.
    Burn Distribution
    Step-by-Step Solution

    Introduction

    This TBSA calculator estimates how much of the body is burned. TBSA stands for Total Body Surface Area. It uses the Rule of Nines, a fast method that gives each body part a set percentage, like 9% for one arm and 18% for one leg.

    Pick each burned area and choose how much of it is burned. You can also set the burn depth:

    • Superficial (1st degree): red skin, no blisters
    • Partial thickness (2nd degree): blisters and pain
    • Full thickness (3rd degree): deep damage through the skin

    The calculator adds up your choices and shows the total TBSA, the critical TBSA (partial and full thickness burns only), and a severity level. Superficial burns are left out of the critical number because doctors do not count them when planning burn care and fluids.

    You also get a body map, charts, and a step-by-step breakdown, so you can see exactly how the total was found. This tool is for learning and quick estimates. Real burn care must always come from a trained medical team.

    How to use our TBSA Burn Calculator

    Pick how much of each body part is burned, then set the burn depth. The calculator shows your total TBSA (total body surface area) burned, the critical TBSA, a severity level, a body map, charts, and the full math.

    Head & Face: Choose 0%, 4.5% (half burned), or 9% (all burned).

    Torso (Front): Choose 0%, 9% (half burned), or 18% (all burned).

    Back: Choose 0%, 9% (half burned), or 18% (all burned).

    Right Arm: Choose 0%, 4.5% (one side burned), or 9% (whole arm burned).

    Left Arm: Choose 0%, 4.5% (one side burned), or 9% (whole arm burned).

    Genital Area: Choose 0% or 1%.

    Right Leg: Choose 0%, 9% (one side burned), or 18% (whole leg burned).

    Left Leg: Choose 0%, 9% (one side burned), or 18% (whole leg burned).

    Burn depth (optional): After you pick a percent, choose Superficial (1st degree), Partial (2nd degree), or Full (3rd degree). Only partial and full burns count toward critical TBSA. Click the same depth again to clear it.

    Calculate: Click this to update your results. Results also refresh each time you tap a button.

    Clear All / Reset: Click this to set every body part back to 0% and start a new burn assessment.

    What Is TBSA in Burns?

    TBSA stands for Total Body Surface Area. It is the percent of a person's skin that is burned. Doctors and nurses use this number to judge how bad a burn is, how much fluid the patient needs, and whether the patient should go to a burn center.

    The Rule of Nines

    The Rule of Nines is a fast way to estimate TBSA in adults. It splits the body into parts that are each about 9% of the skin, or a multiple of 9%.

    • Head and face: 9% (4.5% front, 4.5% back)
    • Front of the torso (chest and belly): 18%
    • Back: 18%
    • Each arm: 9% (4.5% front, 4.5% back)
    • Each leg: 18% (9% front, 9% back)
    • Genital area: 1%

    Add up only the parts that are burned. That total is the TBSA. Children have bigger heads and smaller legs, so kids need a different chart, like the Lund and Browder chart.

    Burn Depth

    Depth tells how far the burn went into the skin. It matters as much as size.

    • Superficial (first degree): Only the top skin layer. Red, dry, and sore, like a sunburn. It heals on its own.
    • Partial thickness (second degree): Goes deeper. Blisters, wet skin, and a lot of pain.
    • Full thickness (third degree): Burns through all skin layers. Looks white, leathery, or charred and may feel numb. It needs surgery or skin grafts.

    First degree burns are left out of the TBSA number used for treatment. Only partial and full thickness burns count toward the "critical" TBSA that guides fluids and transfer to a burn center.

    What the Numbers Mean

    • Under 10%: Minor burn. Often treated at home or in a clinic.
    • 10% to 19%: Moderate burn. Usually needs a hospital stay.
    • 20% to 39%: Major burn. Needs a burn center and IV fluids.
    • 40% to 59%: Critical burn. Life threatening, needs intensive care.
    • 60% and above: Very high risk of death, even with the best care.

    Big burns leak fluid and cause shock. That is why burns over about 20% TBSA in adults get fluid resuscitation, often figured with the Parkland formula.

    Other Quick Methods

    For small or patchy burns, the palm method works well. The patient's palm plus fingers is about 1% of their body surface. Count how many palm sizes the burn covers.

    Warning Signs That Need Care Right Away

    • Burns on the face, hands, feet, joints, or genitals
    • Burns that go all the way around an arm, leg, or the chest
    • Soot around the nose or mouth, a hoarse voice, or trouble breathing
    • Electrical or chemical burns
    • Any full thickness burn

    This tool is for learning and quick estimates only. It does not replace a real exam by a doctor or nurse. Burn size should always be checked again after the patient reaches the hospital.

    Formulas used

    Total TBSA Burned
    \text{TBSA}_{\text{total}} = \sum_{i} P_i
    Critical TBSA (partial + full thickness only)
    \text{TBSA}_{\text{critical}} = \sum_{i \,\in\, \{\text{partial},\ \text{full}\}} P_i
    Excluded (superficial or unclassified) TBSA
    \text{TBSA}_{\text{excluded}} = \text{TBSA}_{\text{total}} - \text{TBSA}_{\text{critical}}
    Unburned body surface
    \text{Unburned} = 100\% - \text{TBSA}_{\text{total}}
    Severity classification from Total TBSA
    \text{Severity} = \begin{cases} \text{Minor}, & 0\% < \text{TBSA}_{\text{total}} < 10\% \\ \text{Moderate}, & 10\% \le \text{TBSA}_{\text{total}} < 20\% \\ \text{Major}, & 20\% \le \text{TBSA}_{\text{total}} < 40\% \\ \text{Critical}, & 40\% \le \text{TBSA}_{\text{total}} < 60\% \\ \text{Potentially Fatal}, & \text{TBSA}_{\text{total}} \ge 60\% \end{cases}
    Rule of Nines region values
    P_i \in \{0,\ 4.5,\ 9\}\ \text{(head, arms)};\quad P_i \in \{0,\ 9,\ 18\}\ \text{(torso, back, legs)};\quad P_i \in \{0,\ 1\}\ \text{(genitals)}

    Frequently asked questions

    How do you calculate IV fluid for a burn patient with the Parkland formula?

    The Parkland formula uses weight and TBSA:

    4 mL × body weight (kg) × %TBSA = total fluid for the first 24 hours.

    Give half in the first 8 hours from the time of the burn, and the rest over the next 16 hours. The fluid is usually Lactated Ringer's.

    Example: a 70 kg adult with 30% TBSA needs 4 × 70 × 30 = 8,400 mL in 24 hours, with 4,200 mL in the first 8 hours.

    Many burn centers now start adults at 2 mL/kg/%TBSA and adjust the rate by urine output. Only partial and full thickness burns count in the %TBSA.

    What is the Rule of Nines for babies and children?

    Kids have big heads and short legs, so the adult chart does not fit. For an infant:

    • Head: 18%
    • Each leg: 14%
    • Each arm: 9%
    • Front torso: 18%
    • Back: 18%

    A common shortcut: for every year over age 1, take 1% off the head and add 0.5% to each leg, until the numbers match an adult around age 10.

    How can you tell a second degree burn from a third degree burn?

    Look at color, feel, and pain.

    • Second degree (partial thickness): blisters, wet or shiny skin, pink or red, turns white when pressed, and hurts a lot.
    • Third degree (full thickness): dry, leathery, white, brown, or charred. It does not blanch when pressed and often feels numb because the nerves are destroyed.

    A burn that does not hurt is a bad sign, not a good one.

    Which burns need to be sent to a burn center?

    Standard referral rules include:

    • Partial thickness burns over 10% TBSA
    • Any full thickness burn
    • Burns on the face, hands, feet, genitals, perineum, or major joints
    • Electrical or chemical burns
    • Inhalation injury (smoke, soot, hoarse voice)
    • Burns in children at hospitals with no pediatric care
    • Burns in people with other injuries or serious medical problems

    Does sunburn count toward TBSA?

    No. Sunburn is usually a superficial (first degree) burn, and first degree burns are left out of the TBSA used for fluids and burn center transfer.

    Only partial thickness and full thickness burns are counted. If the sunburn blisters, it is second degree and does count.

    Why do large burns need IV fluids?

    Burned skin lets fluid leak out of the blood vessels into the tissue. Over about 20% TBSA in adults, this leak happens all over the body, not just at the burn. Blood pressure drops and organs lose blood flow. This is called burn shock.

    IV fluid replaces what is lost. Doctors check if it is working by watching urine output, usually aiming for about 0.5 mL/kg/hour in adults.

    Is the Rule of Nines accurate?

    It is a quick estimate, not an exact number. First responders and doctors who do not work in burns often overestimate burn size, sometimes by two times.

    Too much fluid causes swelling and breathing problems, so burn size should always be re-checked at the hospital using a Lund and Browder chart or a mapping program.

    What is the Baux score for burns?

    The Baux score predicts risk of death from a burn:

    Age + %TBSA burned

    The revised score adds 17 points if there is an inhalation injury. Higher numbers mean higher risk. Older charts called a score near 100 nearly always fatal, but modern burn care has pushed survival much higher.

    What is a circumferential burn and why is it dangerous?

    A circumferential burn wraps all the way around an arm, leg, finger, neck, or the chest. As the burned skin (eschar) gets stiff and the limb swells, it acts like a tight band.

    On a limb it can cut off blood flow. On the chest it can stop the lungs from expanding. Treatment is an escharotomy, a cut through the burned skin to release the pressure.

    How long do burns take to heal?

    • Superficial (1st degree): 3 to 7 days, no scar.
    • Superficial partial thickness: 1 to 3 weeks, usually little or no scar.
    • Deep partial thickness: over 3 weeks, often scars and may need a graft.
    • Full thickness (3rd degree): will not heal on its own and needs a skin graft.

    Any burn taking longer than 2 to 3 weeks should be seen by a burn specialist.

    Does the Rule of Nines work for people with obesity?

    Not well. In people with a higher body weight, the trunk makes up a larger share of the skin, while the head and arms make up a smaller share. Using the standard chart can overestimate limb burns and underestimate trunk burns.

    Burn centers use adjusted charts, sometimes called the rule of fives, plus weight-based fluid limits, to keep the estimate closer to the truth.

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