What is the rule of nines?
The rule of nines is a quick bedside method for estimating the percentage of total body surface area (%TBSA) that is burned. It divides the adult body into regions that are each 9% or a multiple of 9%, with the perineum making up the final 1%. The estimate drives almost every early burn decision — the need for IV fluids, the Parkland volume, and referral to a burn centre.
The concept was first discussed by Pulaski and Tennison in 1949, and A. B. Wallace popularised it in The Lancet in 1951 — which is why exams call it Wallace's rule of nines. It is deliberately crude: Schwartz describes it as 'crude but quick and effective'.
What are the rule of nines percentages in an adult?
| Region | Whole region | Front (anterior) | Back (posterior) |
|---|---|---|---|
| Head and neck | 9% | 4.5% | 4.5% |
| Each upper limb | 9% | 4.5% | 4.5% |
| Trunk — front (chest 9% + abdomen 9%) | 18% | 18% | — |
| Trunk — back (upper back 9% + lower back 9%) | 18% | — | 18% |
| Each lower limb | 18% | 9% | 9% |
| Perineum / genitalia | 1% | — | — |
| Total | 100% |
Add it up: head 9 + two arms 18 + trunk 36 + two legs 36 + perineum 1 = 100%. A handy derivation for partial regions: each lower limb is 18%, so the thigh alone (front + back) is 9%, and the front of one thigh is 4.5%. The face alone is the front half of the head — 4.5%.
How is burn area estimated in children — rule of nines or Lund-Browder?
Infants and young children have proportionately larger heads and smaller legs, so the adult rule of nines is prone to error. A simple paediatric modification gives the head 18% and each leg 13.5%. The more accurate method is the Lund and Browder chart, which adjusts the head and leg percentages for age. Getting this right matters more in children because they have smaller circulating blood volumes, a greater surface-area-to-mass ratio and thinner skin than adults (StatPearls).
| Region | Adult (rule of nines) | Child (modified rule of nines) | Lund-Browder (children) |
|---|---|---|---|
| Head | 9% | 18% | Varies with age — largest in infants, falls as the child grows |
| Each upper limb | 9% | 9% | About 10% (StatPearls) |
| Front of trunk | 18% | 18% | About 13% |
| Back of trunk | 18% | 18% | About 13% |
| Each lower limb | 18% | 13.5% | Varies with age — smallest in infants, rises with growth |
For babies weighing under 10 kg, a 'rule of eights' has also been proposed (about 32% trunk, 20% head, 16% each leg, 8% each arm). In obese adults the trunk is closer to 50% TBSA and each leg about 15%, so limb burns are overestimated and trunk burns underestimated by the standard rule.
What is the palm method (rule of palms)?
For small or scattered (patchy) burns, use the patient's own hand as a ruler. The palmar surface of the patient's hand including the fingers is about 1% TBSA (Schwartz; StatPearls). The palm alone, excluding the fingers, is about 0.5%.
Combine methods when needed: whole regions by the rule of nines, scattered patches by palms. Example: whole right arm (9) + whole left leg (18) + perineum (1) + one palm-sized chest patch (1) = 29%.
Which burns are counted in TBSA, and how is burn depth classified?
Only partial-thickness (second-degree) and full-thickness (third-degree) burns are included in %TBSA. Superficial (first-degree) burns — like sunburn — are excluded. Schwartz adds that soot and debris must be cleaned off so dirty skin is not mistaken for burn.
| Depth | Layers involved | Appearance | Pain / blanching | Healing |
|---|---|---|---|---|
| Superficial (1st degree) | Epidermis only | Pink-red, dry, no blisters | Painful; blanches | 5–10 days, no scar — not counted in TBSA |
| Superficial partial-thickness (2nd) | Epidermis + superficial (papillary) dermis | Red/pink, moist, blisters | Very painful; blanches with pressure | 2–3 weeks, minimal scarring |
| Deep partial-thickness (2nd) | Into the deeper reticular dermis | Mottled pink-white, may blister | Less painful (pressure only); sluggish blanching | Slow; scarring unavoidable; often needs excision and grafting |
| Full-thickness (3rd) | Whole epidermis and dermis, into subcutaneous tissue | White, brown or charred; leathery, stiff, dry | Painless; does not blanch | > 8 weeks; needs surgery (excision and grafting) |
| 4th degree | Beyond skin into fascia, muscle or bone | Charred, deep tissue exposed | Painless | Reconstruction as well as grafting |
How does TBSA feed into the Parkland formula?
Parkland: Ringer's lactate (mL) in first 24 h = 4 × body weight (kg) × %TBSA burned
Give half in the first 8 hours counted from the time of the burn, and the remaining half over the next 16 hours.
Worked example: a 70-kg adult with 40% partial- and full-thickness burns needs 4 × 70 × 40 = 11,200 mL in 24 hours — 5,600 mL in the first 8 hours from injury (not from arrival) and 5,600 mL over the next 16 hours. If the patient arrives 3 hours after the burn, the first half must be given over the remaining 5 hours.
| Item | Value | Source |
|---|---|---|
| Fluid | Lactated Ringer's (crystalloid) | StatPearls — Parkland Formula |
| Threshold for formula-based resuscitation | > 20% TBSA adults; > 10% children (deep partial/full thickness) | StatPearls — Parkland Formula |
| Urine output target — adults | 0.5–1 mL/kg/h | StatPearls — Parkland Formula |
| Urine output target — children | 1.0–1.5 mL/kg/h (children < 30 kg: > 1 mL/kg/h) | StatPearls — Parkland Formula; Rule of Nines |
| Children | Add maintenance fluid on top of the calculated volume (hypoglycaemia risk) | StatPearls — Parkland Formula |
| Modified Brooke formula | 2 mL × kg × %TBSA | StatPearls — Parkland Formula |
| Range quoted in surgical texts | Parkland 3–4 mL/kg/%; American Burn Association consensus 2 mL/kg/% of Ringer's lactate | Schwartz's Surgery |
How do you solve rule of nines and Parkland calculation questions?
| Burned areas | Breakdown | %TBSA |
|---|---|---|
| Both upper limbs + front of chest + front of abdomen | 9 + 9 + 9 + 9 | 36% |
| Entire anterior trunk + whole left arm + circumferential left thigh | 18 + 9 + 9 | 36% |
| Whole right arm + whole left leg + perineum + one palm-sized patch | 9 + 18 + 1 + 1 | 29% |
| Face + both upper limbs + anterior chest | 4.5 + 18 + 9 | 31.5% |
| Front of both lower limbs + front of trunk | 9 + 9 + 18 | 36% |
Parkland worked examples. (1) A 30-kg child with 15% TBSA (above the > 10% paediatric threshold): 4 × 30 × 15 = 1,800 mL in 24 h → 900 mL in the first 8 h, plus maintenance fluid on top because the patient is a child. (2) Asked only for the constant in the classic Parkland formula → 4 mL/kg/%TBSA; 2 mL/kg/%TBSA is the modified Brooke formula.
Monitoring question. The most reliable bedside guide to adequate resuscitation is hourly urine output through a urinary catheter — 0.5–1 mL/kg/h in adults and about 1–1.5 mL/kg/h in children — rather than blood pressure alone.
What are the common rule of nines exam traps?
- Face = 4.5%, not 9%; the whole head and neck is 9%.
- Thigh (circumferential) = 9%; the whole lower limb is 18%; front of the whole leg = 9%.
- Front of chest = 9%; front of abdomen = 9%; the whole anterior trunk = 18%.
- Perineum = 1% — easy to forget.
- Do not count superficial (first-degree) burns or erythema in %TBSA.
- Children — use Lund-Browder; the head is relatively bigger and the legs smaller.
- Palm with fingers ≈ 1% of the patient's own TBSA.
- Parkland 8 hours are from the time of burn, not from hospital arrival.
- Head and neck burns are dangerous mainly because of airway (inhalation) injury — singed eyebrows or facial hair should prompt airway assessment.