About the Burn Surface Area Calculator
This calculator estimates the percentage of total body surface area (%TBSA) affected by a burn. For each body region you enter roughly how much of that region is burned, and the tool weights it by the share of the body that region represents. You can use the adult rule of nines (Wallace), which divides the body into areas of about 9% each, or the Lund–Browder chart, which adjusts the head and leg proportions for age and is the more accurate method — especially in children, whose heads are relatively larger and legs smaller.
Only partial-thickness and full-thickness burns should be counted. Superficial (first-degree) burns that are red but not blistered are excluded from %TBSA, because they do not cause the fluid shifts that make %TBSA clinically important. For small or patchy burns, the palm method is often quicker: the patient’s palm including the fingers is roughly 1% TBSA (measured at about 0.8% in adult men and 0.7% in adult women).
The result is used by emergency, burn and prehospital teams to communicate burn size, apply burn-centre referral criteria and feed resuscitation formulas such as Parkland. Initial estimates are frequently inaccurate — commonly overestimated for small burns — so reassess after cleaning and deroofing blisters, and use a Lund–Browder chart for children.
With the default inputs, the total body surface area burned is 18%. Change any value above to recalculate instantly.
How to use the burn surface area calculator
- 1Choose the rule of nines for a quick adult estimate, or Lund–Browder for children and greater accuracy.
- 2If using Lund–Browder, pick the patient’s age group.
- 3For each region, enter what percentage of that region has partial- or full-thickness burns.
- 4Leave superficial (red, unblistered) burns out of the estimate.
- 5Read the total %TBSA and check the region table; reassess once the wounds have been cleaned.
Formula and method
Each region is assigned its share of total body surface area, and the share is multiplied by the fraction of that region that is burned. With the rule of nines, the head and neck and each arm are 9%, the front and back of the trunk 18% each, each leg 18% and the perineum 1%.
The Lund–Browder chart fixes most areas (anterior trunk 13%, posterior trunk 13% plus 2.5% per buttock, each arm 9.5% including the hand, each foot 3.5%, neck 2%, genitalia 1%) but varies the head, thighs and lower legs with age: at birth half the head is 9.5%, half a thigh 2.75% and half a lower leg 2.5%; in adults these are 3.5%, 4.75% and 3.5%. The calculator uses the values printed on the standard chart (as reproduced in the BMJ ABC of Burns) and groups them into the same eight regions as the rule of nines. Note that the printed 10-year column (half thigh 4½%) adds up to 101%, so whole-body totals are capped at 100%.
- %TBSA
- Percentage of total body surface area with partial- or full-thickness burns
- A, B, C
- Lund–Browder age-dependent values for half the head, half one thigh and half one lower leg
Worked examples
Adult: half the front of the trunk and one whole arm
With the rule of nines the anterior trunk is 18%, so half of it is 9%. The whole right arm adds another 9%, for a total of 18% TBSA.
Adult legs with Lund–Browder
In the adult Lund–Browder chart each leg (thigh 9.5% + lower leg 7% + foot 3.5%) is 20%. One full leg plus half the other gives 20 + 10 = 30% TBSA, slightly more than the 27% the rule of nines would give.
Infant scald to head and chest
An infant’s head is 19% plus 2% for the neck, so a burn covering the whole head and neck is 21%. Half the anterior trunk (13%) adds 6.5%, giving 27.5% TBSA — far more than an adult chart would suggest for the same areas.
Frequently asked questions
What is the rule of nines for burns?+
The rule of nines divides an adult body into regions of about 9%: head and neck 9%, each arm 9%, front of trunk 18%, back of trunk 18%, each leg 18% and the perineum 1%. It gives a fast estimate of burn size in adults.
Why use the Lund–Browder chart instead?+
A child’s head is proportionally much larger and the legs smaller than an adult’s. The Lund–Browder chart adjusts the head, thigh and lower-leg percentages by age, so it is more accurate in children and is preferred by burn units for all ages.
Do first-degree burns count towards %TBSA?+
No. Superficial (first-degree) burns that are red and painful but not blistered are excluded. Only partial-thickness (second-degree) and full-thickness (third-degree) burns are included in the %TBSA used for referral and fluid decisions.
What is the palm method?+
The patient’s palm including the fingers is roughly 1% of their body surface area (measurements put it at about 0.8% in adult men, 0.7% in women and 0.9% in children). It is useful for small or scattered burns: count how many of the patient’s palms would cover the burned area.
How accurate are burn size estimates?+
Not very. Estimates vary between assessors, and with the Lund–Browder chart inter-rater error tends to overestimate small burns and underestimate large ones; the palm method also overestimates. Wrongly counting superficial (red, unblistered) skin inflates early estimates. Accuracy improves after wounds are cleaned and with repeat assessment by experienced staff.
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.
Sources
- Hettiaratchy S, Papini R. ABC of burns — Initial management of a major burn: II, assessment and resuscitation (with Lund and Browder chart). BMJ 2004;329:101–3 (PMC)
- Burn Size Estimation: A Critical Component of Burn Care. Eplasty 2023 (PMC)
- Updating the Burn Center Referral Criteria: Results From the 2018 eDelphi Consensus Study. J Burn Care Res 2020 (PMC)