Summary
Body surface area (BSA) is used for pediatric drug dosing when the dose is defined per square meter, most importantly for chemotherapy. It is preferred over weight-based dosing for agents with a narrow therapeutic index because it correlates more closely with metabolic rate, cardiac output, and glomerular filtration than weight alone [4].
- Haycock is the reference formula in pediatric oncology and performs well in infants and small children [1].
- Mosteller is a simpler estimate, is built into most electronic health records, and is adequate above 20 kg [2].
- Most non-oncology pediatric drugs are dosed per kilogram, not per square meter. Match the protocol.
- Burn resuscitation is dosed by weight and percent total body surface area burned, with the burned area estimated from an age-adjusted Lund-Browder chart [5].
Caution. For a drug with a narrow therapeutic index, a 10% BSA error can move a patient from effective therapy into toxicity, or into undertreatment. Calculate BSA independently and have a second clinician verify it before a cytotoxic order is signed.
Formulas
| Formula |
Equation (BSA in m²) |
Notes |
| Haycock |
0.024265 × Weight(kg)^0.5378 × Height(cm)^0.3964 |
Pediatric oncology reference; validated in infants and children [1] |
| Mosteller |
√[Height(cm) × Weight(kg) / 3600] |
Fast bedside estimate; in most EHRs [2] |
| DuBois & DuBois |
0.007184 × Height(cm)^0.725 × Weight(kg)^0.425 |
Historical; underestimates BSA in small children [3] |
The three formulas diverge most in the youngest children. Use one formula consistently for serial dosing in a given patient, and do not switch mid-course.
Compare formulas in the BSA Calculator →
Clinical pearl. For a 3-year-old, 15 kg, 96 cm: Haycock gives 0.024265 × 15^0.5378 × 96^0.3964 = 0.64 m²; Mosteller gives √[(96 × 15) / 3600] = 0.63 m². Methotrexate at 1 g/m² is therefore a 0.64 g dose by Haycock.
Indications
| Setting |
Basis |
Representative dosing |
| Chemotherapy |
Narrow therapeutic index; standard doses defined per m² [4] |
Doxorubicin, cisplatin, methotrexate all per m² |
| High-dose cardiovascular agents |
More predictable hemodynamic response across body sizes |
Selected inotropes and vasodilators |
| Dialysis adequacy |
Clearance targets indexed to body size |
Kt/V and clearance normalized to BSA |
Use weight-based (per-kilogram) dosing when the drug reference defines the dose per kilogram, which is the case for most non-oncology pediatric medications.
Burn resuscitation
The Parkland formula estimates the first 24 hours of resuscitation fluid as 4 mL × percent total body surface area burned × weight (kg), with half in the first 8 hours and the remainder over the next 16 hours [5]. The result is only as good as the burned-area estimate.
Body proportions change with age, so the adult rule of nines overestimates burned area from the legs and underestimates it from the head in young children. In infants the head is a larger share of total surface area and the legs a smaller share than in adults. Use an age-adjusted Lund-Browder chart [5].
Estimate burned area and plan fluid in Parkland Burns →
Special populations
Obesity. Dosing on actual body weight can overshoot in an obese child, because fat contributes less to the volume of distribution of many drugs than lean mass does. The correct descriptor (actual, ideal, or adjusted body weight, or BSA) is drug- and protocol-specific. Confirm which the protocol specifies before dosing.
Short stature. The Devine ideal-body-weight formula was derived in adults and applies only at heights of at least 152 cm (5 feet) [6]. For shorter or younger children, use a BMI-based method or the institutional ideal-body-weight protocol.
Estimate ideal and adjusted body weight in Ideal Body Weight →
References
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: A height-weight formula validated in infants, children, and adults. J Pediatr. 1978;93(1):62-66. doi:10.1016/s0022-3476(78)80601-5
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098. doi:10.1056/NEJM198710223171717
- DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863-871.
- Gurney H. How to calculate the dose of chemotherapy. Br J Cancer. 2002;86(8):1297-1302. doi:10.1038/sj.bjc.6600139
- Romanowski KS, Palmieri TL. Pediatric burn resuscitation: past, present, and future. Burns Trauma. 2017;5:26. doi:10.1186/s41038-017-0091-y
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650-655.