Clinical calculator

Body Surface Area and Body Weight Calculator

A browser-only educational calculator for BSA, ideal body weight, and adjusted body weight. Information entered on this page is not saved or stored by RPHprep.

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RPHprep provides educational exam-preparation content only. It is not medical advice, legal advice, or a substitute for professional judgment. Users should consult current Canadian laws, standards, guidelines, product monographs, and official regulatory resources.

Information you record on this page is not saved or stored. Print or send before leaving this page to avoid losing the information you enter.

Only digits 0 to 9 and a single decimal point are acceptable as numeric inputs.

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Body size inputs

Sex

Formulas

Mosteller BSA = sqrt(height(cm) * weight(kg) / 3600)

Haycock BSA = 0.024265 * height(cm)^0.3964 * weight(kg)^0.5378

ABW = IBW + 0.4 * (actual weight - IBW)

Calculation notes

The ideal body weight equations used here classify patients as male or female. RPHprep recognizes that these terms may not accurately reflect the identity of every person and may not be inclusive of all individuals. Each person should be assessed on an individual basis.

Adjusted body weight is calculated as IBW plus 0.4 times the difference between actual body weight and IBW. Some references discuss this approach for aminoglycoside dosing in individuals with obesity when total body weight is more than 25% above IBW.

References

  1. Mosteller RD. Simplified calculation of body surface area. N Engl J Med. 1987;317(17):1098.
  2. 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.
  3. Green B, Duffull SB. What is the best size descriptor to use for pharmacokinetic studies in the obese? Br J Clin Pharmacol. 2004;58(2):119-133.
  4. Traynor AM, Nafziger AN, Bertino JS. Aminoglycoside dosing weight correction factors for patients of various body sizes. Antimicrob Agents Chemother. 1995;39(2):545-548.