TBSA Burn Calculator - Rule of Nines, Burn Depth, Severity

Q: 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 4 = 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. 11 The fluid is usually Lactated Ringer's. 4 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. The American Burn Association's guideline recommends starting adults at 2 mL/kg/%TBSA to reduce fluid volumes. 5 The rate is then adjusted by urine output. Only partial and full thickness burns count in the %TBSA. 1

Q: 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.

Q: 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. 1 Third degree (full thickness): dry, leathery, white, brown, or charred. 1 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. 3

Q: Which burns need to be sent to a burn center?

The American Burn Association's referral guidelines call for an immediate burn center consult for: Partial thickness burns of 10% TBSA or more 1 Any full thickness burn Deep partial or full thickness burns of the face, hands, feet, genitals, perineum, or any joint Chemical burns High voltage electrical burns of 1,000 volts or more, and lightning injuries 1 Suspected inhalation injury Burns in people with other injuries, serious medical problems, or pain that is hard to control They add that all burns in children may benefit from burn center referral. 1

Q: 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. 1 Only partial thickness and full thickness burns are counted. 1 If the sunburn blisters, it is second degree and does count. 1

Q: 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. 11

Q: Is the Rule of Nines accurate?

It is a quick estimate, not an exact number. 1 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.

Q: What is the Baux score for burns?

The Baux score predicts risk of death from a burn: Age + %TBSA burned 6 The revised score adds 17 points if there is an inhalation injury. 6 Higher numbers mean higher risk. Older charts treated a score near 100 as nearly always fatal. Advances in burn care have made the original score's predictions too pessimistic. 6

Q: 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. 8 Treatment is an escharotomy , a cut through the burned skin to release the pressure. 8

Q: How long do burns take to heal?

Superficial (1st degree): heals without scarring within 5 to 10 days. 10 Superficial partial thickness: heals within 2 to 3 weeks with minimal scarring. 10 Deep partial thickness: can heal without surgery, but it takes longer and scarring is unavoidable. 10 Full thickness (3rd degree): takes more than 8 weeks to heal and needs surgical treatment. 10 Any burn taking longer than 2 to 3 weeks should be seen by a burn specialist.

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.¹

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

Superficial (first degree): red skin, no blisters³
Partial thickness (second degree): blisters and pain³
Full thickness (third degree): deep damage through the skin³

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.¹

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.¹

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%.¹

Head and face: 9% (4.5% front, 4.5% back)²
Front of the torso (chest and belly): 18%²
Back: 18%²
Each arm: 9% (4.5% front, 4.5% back)²
Each leg: 18% (9% front, 9% back)²
Genital area: 1%²

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.¹

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.³ Red, dry, and sore, like a sunburn.¹ It heals on its own.³
Partial thickness (second degree): Goes deeper. Blisters, wet skin, and a lot of pain.¹
Full thickness (third degree): Burns through all skin layers. Looks white, leathery, or charred and may feel numb.¹ It takes more than 8 weeks to heal and needs surgical treatment.¹⁰

First degree burns are left out of the TBSA number used for treatment.¹ Only partial and full thickness burns count toward the "critical" TBSA that guides fluids and transfer to a burn center.²

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 adults with burns of about 20% TBSA or more get fluid resuscitation.⁵ The Parkland formula is the one used most often to plan it.⁴

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.⁹ Count how many palm sizes the burn covers.

Warning Signs That Need Care Right Away

Burns on the face, hands, feet, joints, or genitals¹
Burns that go all the way around an arm, leg, or the chest⁸
Soot around the nose or mouth, a hoarse voice, or trouble breathing³
Electrical or chemical burns¹
Any full thickness burn¹

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 burned area, superficial burns not counted

\text{TBSA}_{\text{graded}} = \text{TBSA}_{\text{total}} - \text{TBSA}_{\text{superficial}};\quad \text{Severity} = \begin{cases} \text{Minor}, & 0\% < \text{TBSA}_{\text{graded}} < 10\% \\ \text{Moderate}, & 10\% \le \text{TBSA}_{\text{graded}} < 20\% \\ \text{Major}, & 20\% \le \text{TBSA}_{\text{graded}} < 40\% \\ \text{Critical}, & 40\% \le \text{TBSA}_{\text{graded}} < 60\% \\ \text{Potentially Fatal}, & \text{TBSA}_{\text{graded}} \ge 60\% \end{cases}

Rule of Nines region values ²

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) × %TBSA⁴ = 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.¹¹ The fluid is usually Lactated Ringer's.⁴

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.

The American Burn Association's guideline recommends starting adults at 2 mL/kg/%TBSA to reduce fluid volumes.⁵ The rate is then adjusted by urine output. Only partial and full thickness burns count in the %TBSA.¹

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.¹
Third degree (full thickness): dry, leathery, white, brown, or charred.¹ 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.³

Which burns need to be sent to a burn center?

The American Burn Association's referral guidelines call for an immediate burn center consult for:

Partial thickness burns of 10% TBSA or more¹
Any full thickness burn
Deep partial or full thickness burns of the face, hands, feet, genitals, perineum, or any joint
Chemical burns
High voltage electrical burns of 1,000 volts or more, and lightning injuries¹
Suspected inhalation injury
Burns in people with other injuries, serious medical problems, or pain that is hard to control

They add that all burns in children may benefit from burn center referral.¹

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.¹

Only partial thickness and full thickness burns are counted.¹ If the sunburn blisters, it is second degree and does count.¹

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.¹¹

Is the Rule of Nines accurate?

It is a quick estimate, not an exact number.¹ 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 burned⁶

The revised score adds 17 points if there is an inhalation injury.⁶ Higher numbers mean higher risk. Older charts treated a score near 100 as nearly always fatal. Advances in burn care have made the original score's predictions too pessimistic.⁶

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.⁸ Treatment is an escharotomy, a cut through the burned skin to release the pressure.⁸

How long do burns take to heal?

Superficial (1st degree): heals without scarring within 5 to 10 days.¹⁰
Superficial partial thickness: heals within 2 to 3 weeks with minimal scarring.¹⁰
Deep partial thickness: can heal without surgery, but it takes longer and scarring is unavoidable.¹⁰
Full thickness (3rd degree): takes more than 8 weeks to heal and needs surgical treatment.¹⁰

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 and legs make up a larger share of the skin, while the head and arms make up a smaller share. The rule of nines gives reasonable estimates from 10 to 80 kg.⁷

For patients over 80 kg, researchers proposed a rule of fives: 5% for each arm, 20% for each leg, 50% for the trunk, and 2% for the head.⁷

Sources

Guidelines for Burn Patient Referral. American Burn Association. Accessed September 26, 2026.

Moore RA, Popowicz P. Rule of Nines. StatPearls Publishing. 2024. Accessed September 26, 2026.

Burns. MedlinePlus, U.S. National Library of Medicine. Accessed September 26, 2026.

Mehta M. Parkland Formula. StatPearls Publishing. 2023. Accessed September 26, 2026.

Cartotto R, Johnson LS, Savetamal A, Greenhalgh D, Kubasiak JC, Pham TN, Rizzo JA, Sen S, Main E. American Burn Association Clinical Practice Guidelines on Burn Shock Resuscitation. Journal of Burn Care & Research. 2024;45(3):565-589. doi:10.1093/jbcr/irad125. Accessed September 26, 2026.

Osler T, Glance LG, Hosmer DW. Simplified estimates of the probability of death after burn injuries: extending and updating the Baux score. Journal of Trauma. 2010;68(3):690-697. doi:10.1097/TA.0b013e3181c453b3. Accessed September 26, 2026.

Livingston EH, Lee S. Percentage of burned body surface area determination in obese and nonobese patients. Journal of Surgical Research. 2000;91(2):106-110. doi:10.1006/jsre.2000.5909. Accessed September 26, 2026.

Wang CF. Escharotomy. StatPearls Publishing. 2026. Accessed September 26, 2026.

Determining Total Body Surface Area. Minnesota Department of Health. Accessed September 26, 2026.

Warby R, Maani CV. Burn Classification. StatPearls. StatPearls Publishing. 2023;Definition/Introduction. Accessed October 8, 2026.

Toussaint J, Singer AJ. The evaluation and management of thermal injuries: 2014 update. Clinical and Experimental Emergency Medicine. 2014;1(1):8-18. doi:10.15441/ceem.14.029. Accessed October 8, 2026.

TBSA Calculator

Rate this calculator

Introduction

How to use our TBSA Burn Calculator

What Is TBSA in Burns?

The Rule of Nines

Burn Depth

What the Numbers Mean

Other Quick Methods

Warning Signs That Need Care Right Away

Formulas used

Frequently asked questions

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

What is the Rule of Nines for babies and children?

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

Which burns need to be sent to a burn center?

Does sunburn count toward TBSA?

Why do large burns need IV fluids?

Is the Rule of Nines accurate?

What is the Baux score for burns?

What is a circumferential burn and why is it dangerous?

How long do burns take to heal?

Does the Rule of Nines work for people with obesity?

Sources

TBSA Calculator

Rate this calculator

Introduction

How to use our TBSA Burn Calculator

What Is TBSA in Burns?

The Rule of Nines

Burn Depth

What the Numbers Mean

Other Quick Methods

Warning Signs That Need Care Right Away

Formulas used

Frequently asked questions

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

What is the Rule of Nines for babies and children?

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

Which burns need to be sent to a burn center?

Does sunburn count toward TBSA?

Why do large burns need IV fluids?

Is the Rule of Nines accurate?

What is the Baux score for burns?

What is a circumferential burn and why is it dangerous?

How long do burns take to heal?

Does the Rule of Nines work for people with obesity?

Sources

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