Burn TBSA Calculator (Rule of Nines)

Burned surface area from the rule of nines, with the paediatric age adjustment that exists because a child’s head is twice the adult share. Superficial erythema is excluded, and every downstream volume multiplies this number.

Last updated 8 Oct 2026

Burn total body surface area

Rule of nines, age-adjusted

Age (years)The head and the legs are the only segments that change with age, and they change a lot. Under 15 years this page applies NSW Health’s published adjustment to the paediatric chart — take 1 per cent off the head and add 0.5 per cent to each leg for every year of life, from a baseline of 18 per cent head and 14 per cent per leg — capped at 9 years, where adult proportions are reached.

Head and neck burned (% of that segment)What proportion of the head-and-neck segment is burned, not what proportion of the body. A whole scalp, face and neck is 100 here, which is 9 per cent of an adult’s TBSA and 18 per cent of a newborn’s.

Both arms burned (% of that segment)Both arms together are 18 per cent at every age. One whole arm is therefore 50 here. Circumferential matters clinically but not to this arithmetic — the segment percentage already counts front and back.

Trunk, front and back, burned (% of that segment)Anterior and posterior trunk together are 36 per cent at every age — 18 front, 18 back. A whole anterior trunk is therefore 50 here, not 100.

Both legs burned (% of that segment)Both legs together: 36 per cent in an adult, 28 per cent in a newborn, rising 1 per cent per year of life. One whole leg is 50 here.

Perineum and genitaliaThe adult Wallace chart reserves 1 per cent for the perineum and the four segments above sum to 99. The paediatric chart used here has no separate perineal segment and its four segments already sum to 100, so in a child this option takes the arithmetic to 101 — capped at 100. That seam between two published charts is printed rather than smoothed over.

23.0% TBSAExample

A 4-year-old with the whole head and neck burned and one entire arm burned; no superficial erythema counted

Formula

TBSA = Σ (fraction of each segment burned × that segment’s share of body surface)
Adult, 15 years and over: head and neck 9 · each arm 9 · anterior trunk 18 · posterior trunk 18 · each leg 18 · perineum 1
Under 15: head 18 − (age in years) · each leg 14 + 0.5 × (age in years), capped at 9 years

superficial burns are excluded: the American Burn Association states it without qualification: superficial, sunburn-type burns are “NOT counted in calculations of total burn surface area (TBSA)”. Superficial partial, deep partial and full-thickness burns are counted. NSW Health’s paediatric guidance puts the same rule as “ignore simple erythema”. Including erythema is the classic over-estimate, and it is the one that multiplies straight into the resuscitation volume
the paediatric adjustment, and what it is not: NSW Health’s paediatric burn page gives the under-9 chart as head 18, each arm 9, front torso 18, back torso 18, each leg 14, and the rule “For every year of life, take 1% from the head and add 0.5% to each leg”. That is an age-adjusted RULE OF NINES. It is not the Lund and Browder chart, which bands the head, thighs and lower legs separately by age and is the more accurate instrument
sources disagree on the paediatric bands: Minnesota’s Department of Health publishes age-banded figures that do not match: head 21 per cent and each leg 13.5 under one year, then head 19 and leg 15 at 1 to 4, 15 and 17 at 5 to 9, 13 and 18 at 10 to 14. NSW Health’s rule gives head 18 and leg 14 at birth. Both are printed here; this page implements the NSW rule because it is stated as arithmetic rather than as a table, and a reader comparing against a Minnesota-style chart should expect the head to differ by about 3 percentage points in infancy
the palm rule, and its disagreement: the ABA gives “The patient’s palm is roughly 1% of TBSA”, suited to scattered burns under about 15 to 20 per cent. Minnesota is explicit that this is “The patient’s palmar surface including their fingers = 1% TBSA”. A surgical education source prints both conventions side by side: palm with digits about 1 per cent, palm alone about 0.5 per cent, uncited for either figure. The two differ by a factor of two, so ten scattered patches scored one way rather than the other change TBSA by 5 points — 1.4 litres of Parkland in a 70 kg adult. Use the patient’s hand, not yours, and say which convention you used
what this chart is for: an initial estimate. The ABA says the rule of nines “is most accurate for adults”, that children and infants need adjustments such as the Lund and Browder chart, and that the method is “meant for initial assessment only”. Everything downstream — the Parkland volume, the revised Baux score, the external-region term of the ISS — inherits this number’s error

Worked example

A 4-year-old with the whole head and neck burned and one entire arm burned; no superficial erythema counted
At 4 years the head is 18 − 4 = 14 per cent and each leg is 14 + 2 = 16 per cent
Head and neck 100 per cent burned → 1.00 × 14 = 14.0
One whole arm is 50 per cent of the both-arms segment → 0.50 × 18 = 9.0
Total = 14.0 + 9.0 = 23.0 per cent TBSA
Score the same child on the adult chart and the head contributes 9 instead of 14: total 18.0 per cent. A 5-point under-estimate from using the wrong chart, which is 1.4 litres of Parkland in a 70 kg adult and proportionately as much in a child
Now add a patch of simple erythema over a quarter of the trunk segment. Counted, it would add 0.25 × 36 = 9 points, taking the total to 32.0 — a 39 per cent over-estimate. It is not counted, and that is the single commonest error in burn size

Segment shares of body surface, by age

Paediatric figures from NSW Health’s rule — 18 per cent head and 14 per cent per leg at birth, 1 per cent off the head and 0.5 on to each leg per year, stopping at 9. Adult figures are the Wallace rule of nines. Both columns sum to 100, and the seam at 15 years moves 1 per cent from the legs to the perineum. Minnesota’s Department of Health publishes different infant figures — head 21, each leg 13.5 — and that disagreement is real rather than a transcription error.
Segment	Newborn	Age 4	Age 9 and over (paediatric chart)	Adult, 15 and over
Head and neck	18	14	9	9
Each arm	9	9	9	9
Trunk, front and back	36	36	36	36
Each leg	14	16	18.5	18
Perineum	not a separate segment	not a separate segment	not a separate segment	1
Total	100	100	100	100

What a 5-percentage-point TBSA error costs downstream

Every figure is this batch’s own arithmetic. Five percentage points of TBSA — one limb segment mis-scored, or ten patches counted at 1 per cent on the palm rule instead of 0.5 — is 1.4 litres of crystalloid at the Parkland rate and 5 points of revised Baux. Burn size is the measurement in this chain that is estimated by eye, and it is the one everything else multiplies.
TBSA	Parkland at 4 mL/kg/% in a 70 kg adult	ABA 2023 at 2 mL/kg/%	Revised Baux at age 45
25%	7,000 mL	3,500 mL	70 points
30%	8,400 mL	4,200 mL	75 points
35%	9,800 mL	4,900 mL	80 points
40%	11,200 mL	5,600 mL	85 points

The estimate everything else multiplies

Burn size drives the resuscitation volume, the referral criteria, the mortality estimate and the external-region term of the Injury Severity Score. It is also the only number in that chain that is produced by looking at a patient and judging, and published series find wide variation between assessors. So the discipline around the estimate matters more than the arithmetic that follows it.

The rule of nines divides the adult body into nine-per-cent blocks: head and neck nine, each arm nine, anterior trunk eighteen, posterior trunk eighteen, each leg eighteen, perineum one. It is fast and it is wrong in children, because a small child’s head is a far larger share of the surface and the legs a smaller one. At birth the head is about eighteen per cent — exactly twice the adult figure — and each leg about fourteen. NSW Health’s paediatric guidance states the correction as arithmetic: take one per cent off the head and add half a per cent to each leg for every year of life, until adult proportions are reached at about nine. That is what this page implements, and it is an age-adjusted rule of nines rather than the Lund and Browder chart, which bands the head, thighs and lower legs separately and is the more accurate instrument.

Two things decide whether the number is usable. The first is that superficial burns are excluded. The American Burn Association puts it without qualification: superficial, sunburn-type burns are not counted in TBSA; superficial partial, deep partial and full-thickness burns are. NSW Health’s version is to ignore simple erythema. Including erythema is the classic over-estimate, and because the Parkland formula multiplies TBSA by weight and by four, a few unnecessary percentage points become litres. The second is the palm rule for scattered burns, where the sources genuinely disagree: the ABA and Minnesota’s Department of Health give the patient’s palm including the fingers as about one per cent, while a surgical education source prints palm-with-digits at about one per cent and palm alone at about half a per cent. Those differ by a factor of two. Use the patient’s hand rather than your own, and record which convention you used.

Finally, this is an initial estimate and nothing more. The ABA says the rule of nines is most accurate for adults, that children need a Lund and Browder-type chart, and that the method is meant for initial assessment only. A five-percentage-point error here is 1.4 litres of crystalloid in a seventy-kilogram adult at the Parkland rate, and five points of revised Baux score. Re-estimate after cleaning and debridement, when the depth of the burn is actually visible.

Frequently asked questions

Are superficial burns included in TBSA?

No. The American Burn Association states that superficial, sunburn-type burns are not counted in calculations of total burn surface area; superficial partial, deep partial and full-thickness burns are. NSW Health’s paediatric guidance says the same thing as ignore simple erythema. Counting erythema is the commonest reason a burn is over-estimated, and it feeds straight into the fluid volume.

Why does the rule of nines change in children?

Because body proportions do. A newborn’s head is about 18 per cent of the body surface against an adult’s 9, and each leg about 14 against 18. NSW Health’s correction is to take 1 per cent off the head and add 0.5 per cent to each leg for every year of life, reaching adult proportions at about 9 years. Scoring a small child on the adult chart under-reads a head burn by up to 9 percentage points.

Is the palm 1 per cent or 0.5 per cent of TBSA?

It depends which convention, and the sources disagree. The ABA and Minnesota’s Department of Health give the patient’s palm including the fingers as about 1 per cent. A surgical education source prints palm with digits at about 1 per cent and palm alone at about 0.5 per cent. Since those differ twofold, state which you used — ten scattered patches scored one way rather than the other move TBSA by 5 points.

Is this the Lund and Browder chart?

No. This is an age-adjusted rule of nines, which NSW Health publishes as a piece of arithmetic. The Lund and Browder chart bands the head, thighs and lower legs separately by age and is generally regarded as more accurate; it requires reading a printed age table, and this plugin’s engine cannot interpolate one. Use a Lund and Browder chart where one is available, particularly in small children.

Why does the calculator sometimes cap the total at 100 per cent?

Because the adult and paediatric charts allocate their last 1 per cent differently. The adult Wallace chart’s four body segments sum to 99 and reserve 1 per cent for the perineum; the paediatric chart used here has no separate perineal segment and its four segments already sum to 100. Selecting the perineum in a child therefore reaches 101, which is capped. The seam is printed rather than hidden.

Related calculators

References

American Burn Association. Burn Center Referral Criteria — including that superficial burns are not counted in TBSA. ameriburn.org/burnreferral
Agency for Clinical Innovation. ECAT paediatric assessment: burn. NSW Health. aci.health.nsw.gov.au/ecat/paediatric/assessment/burn
Minnesota Department of Health. Estimating total body surface area burned — adult, child and infant rule-of-nines tables. health.state.mn.us/communities/ep/surge/burn/tbsa.html
The Plastics Fella. Total body surface area calculations in burns — the palm-only and palm-plus-digits figures side by side. theplasticsfella.com/total-body-surface-area-in-burns/
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. J Burn Care Res. 2023. doi:10.1093/jbcr/irad125

Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/