Burn Percentage Calculator

Early intubation should be considered for patients with facial burns, singed nasal hairs, carbonaceous sputum, stridor, hoarseness, or a history of enclosed-space fire exposure. Airway oedema can progress rapidly over the first 12–24 hours and may render delayed intubation extremely difficult. Supplemental 100% oxygen is mandatory for suspected carbon monoxide (CO) or cyanide exposure — CO-oximetry should be obtained, as standard pulse oximetry can give falsely normal readings in CO poisoning.

Escharotomies may be required for circumferential full-thickness burns of the thorax (restricting ventilation) or extremities (causing compartment syndrome). These should be performed emergently and do not require anaesthesia in full-thickness burns, as the tissue is insensate.

Parkland formula (4 mL/kg/%TBSA) is the most widely used initial resuscitation formula. Lactated Ringer’s is the preferred crystalloid. The 24-hour total is divided: half administered in the first 8 hours from the time of injury (not from hospital arrival), and the remaining half over the next 16 hours. If significant time has elapsed between injury and presentation, the first-8-hour portion must be delivered in the remaining time of that window.

Modified Brooke formula (2 mL/kg/%TBSA) is now recommended by ATLS and the ABA consensus statement as a starting point to reduce over-resuscitation. Both formulas are estimates — actual fluid delivery must be titrated to physiological endpoints. Target urine output is 0.5–1.0 mL/kg/h in adults and 1–2 mL/kg/h in children. Colloid (albumin) is typically introduced after the first 24 hours to maintain intravascular volume.

The American Burn Association recommends transfer to a verified burn centre for any of the following:

• Partial-thickness burns >10% TBSA
• Burns involving the face, hands, feet, genitalia, perineum, or major joints
• Full-thickness (third-degree) burns of any size
• Electrical burns (including lightning injury)
• Chemical burns
• Inhalation injury
• Burns in patients with significant comorbidities
• Burns with concomitant trauma where the burn is the greater risk
• Burns in children at hospitals without qualified paediatric capability
• Patients requiring special social, emotional, or rehabilitative support

Inhalation injury significantly increases mortality at any given TBSA — it adds approximately 17 points to the revised Baux score and increases fluid requirements by 30–50% above the Parkland calculation. Suspect inhalation injury in patients with enclosed-space fire, facial/neck burns, carbonaceous deposits in the oropharynx, hoarseness, wheezing, or altered mental status. Definitive diagnosis is by fibreoptic bronchoscopy revealing airway oedema, erythema, or soot deposits below the vocal cords.

Management includes early intubation if airway compromise is anticipated, 100% FiO₂ for CO poisoning (half-life of COHb on room air is ~5 hours, reduced to ~1 hour on 100% O₂), and consideration of hydroxocobalamin for cyanide toxicity in patients with persistent lactic acidosis despite adequate resuscitation.

Superficial (first-degree) burns — such as sunburns — cause erythema without blistering and do not result in significant fluid shifts. Including them in TBSA calculations inflates the estimate and can lead to unnecessary or excessive fluid resuscitation. Only partial-thickness and full-thickness burns should be counted. This is one of the most frequent errors made by non-burn-specialised clinicians, particularly in mixed-depth injuries where superficial areas are adjacent to deeper burns.

Children have proportionally larger heads and smaller legs than adults. An infant’s head is approximately 18% TBSA (vs. 9% in adults), and each leg is approximately 14% (vs. 18%). Using adult percentages in young children can significantly underestimate head burns and overestimate lower limb burns. The Lund-Browder chart adjusts for age-related proportional changes and is the recommended method for paediatric burn assessment. At minimum, clinicians should use the modified paediatric Rule of Nines when the Lund-Browder chart is not readily available.

The Parkland formula provides a starting rate for crystalloid resuscitation — it is not a fixed volume target. Actual fluid requirements depend on burn depth, inhalation injury, delays in resuscitation, patient comorbidities, and physiological response. Clinicians must titrate fluid administration to clinical endpoints: urine output (0.5–1.0 mL/kg/h in adults), mean arterial pressure, heart rate, and lactate clearance. Multiple studies have shown that adherence to the Parkland volume without titration leads to “fluid creep” and significantly worse outcomes.

The Parkland formula specifies that the first half of the 24-hour fluid volume should be delivered within 8 hours from the time of injury, not from hospital presentation. If a patient presents 3 hours after their burn, only 5 hours remain for the first half of resuscitation, requiring a faster infusion rate. This distinction is critical — delays in recognising the correct time window can result in relative under-resuscitation during the period of maximal capillary leak (first 8–12 hours post-injury).

The Rule of Nines works best for large, confluent burns that occupy most of a body region. For scattered or patchy burns — common in scald, splash, and chemical injuries — the Rule of Nines tends to overestimate TBSA because clinicians may assign the full regional percentage to an area that is only partially burned. In these cases, the palmar method (patient’s palm ≈ 1% TBSA) or the Lund-Browder chart should be used to map individual burn patches more accurately. Studies demonstrate inter-rater variability of 10–20% in TBSA estimation, underscoring the need for photographs and telemedicine consultation with burn centres.