Why burn size matters
The share of the body surface that is burned, the total body surface area or TBSA, guides almost every decision in burn care: whether intravenous fluids are needed, how much to give, and whether the patient should go to a burn center. Large burns cause fluid to leak out of blood vessels, and without enough fluid, patients can go into burn shock within hours.
The rule of nines
For adults, the rule of nines divides the body into areas of about 9% or multiples of it:
| Region | Share of the body |
|---|---|
| Head and neck | 9% |
| Each arm | 9% |
| Front of the trunk | 18% |
| Back of the trunk | 18% |
| Each leg | 18% |
| Perineum | 1% |
The calculator multiplies the share of each region that is burned by its weight and adds them up. Only partial-thickness (second-degree) and full-thickness (third-degree) burns count; simple redness is left out.
The Parkland formula
For adults with burns over about 20% of TBSA, the Parkland formula gives a starting estimate of fluid for the first 24 hours:
volume (mL) = 4 × weight (kg) × %TBSA
Half is given in the first 8 hours from the time of the burn, not from arrival, and the other half over the next 16 hours. Many centers now start with 2 to 4 mL per kg per %TBSA and adjust to urine output.
Worked example
A 70 kg adult has burns over half the front of the trunk and the whole right arm:
| Result | Value |
|---|---|
| TBSA burned | 18% (9% + 9%) |
| Parkland volume, 24 hours | 5,040 mL |
| Rate, first 8 hours | 315 mL/h |
| Rate, next 16 hours | 158 mL/h |
Limits
- The rule of nines overestimates small burns and is less accurate for children, whose heads are larger in proportion. The Lund and Browder chart is used for children.
- For scattered burns, the patient’s palm with fingers closed is about 1% of the body surface.
- Formulas only start resuscitation: the rate is adjusted to urine output, typically aiming for about 0.5 mL/kg/h in adults.
- Burns of the face, hands, feet, genitals or major joints, and electrical, chemical or inhalation injuries need specialist care whatever their size.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.