Burn Percentage Calculator (Rule of Nines)
Estimate the total body surface area (TBSA) burned in an adult using the Rule of Nines. Mark each affected body region to add up the percentage burned — a fast emergency estimate used to guide fluid resuscitation. Seek immediate medical care for any significant burn.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Adult proportions. Emergency estimate only — seek immediate medical care for significant burns.
Formula
Adult rule of nines: head 9, each arm 9, each leg 18, front trunk 18, back trunk 18, genitalia 1
- The Rule of Nines divides an adult body into areas that are multiples of 9% of total surface area.
- Head and neck = 9%, each arm = 9%, each leg = 18%, front trunk = 18%, back trunk = 18%, genitalia = 1%.
- Select each region that is burned and the percentages add up to the total TBSA.
- A TBSA of about 15% or more in adults often signals the need for IV fluid resuscitation.
- Children have different proportions (larger heads), so the adult Rule of Nines doesn't apply to them.
One arm plus front trunk
Marking one arm (9%) and the anterior trunk (18%) gives an estimated TBSA of 27% — a large burn needing urgent care.
Frequently asked questions
What is the Rule of Nines?
It's a quick method to estimate the percentage of body surface burned by assigning multiples of 9% to each body region.
Why does TBSA matter?
It guides emergency fluid resuscitation and helps decide whether someone needs transfer to a burn centre.
Does this work for children?
No. Children's body proportions differ, so paediatric burns use the Lund and Browder chart instead.
What counts as a large burn?
In adults, roughly 15% TBSA or more is considered significant and usually needs IV fluids and specialist care.
Is this a diagnosis?
No. It's a rapid field estimate. Any significant burn needs immediate professional medical assessment.
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