Mosteller
Commonly used practical adult default with simple, reproducible calculation.
BSA = √((H × W) / 3600)
Typical use: routine adult perfusion indexing.
BSA Calculator for Perfusion Flow Guidance in CPB
Calculate BSA first, then estimate indexed pump flow targets (CI 1.0-3.0) for clinical perfusion planning.
Body Surface Area
BSA Calculator
Enter height and weight to calculate BSA and perfusion flow guidance.
BSA (m²)
0.00
BSA Output
—
Formula
Mosteller
BMI: —
Quick summary
Body surface area (BSA) is used to normalize CPB flow and perfusion references to patient size. This calculator estimates BSA and provides indexed flow guidance for clinical context.
Formula Comparison
Enter height and weight to compare formulas.
Blood Flow Rate by Cardiac Index
BSA-based adult CPB flow · weight-indexed reference
mL/kg/min is shown as a weight-indexed reference conversion, not a separate adult CPB target.
BMI 25 Reference Flow
Comparison reference only; not an automatic flow target.
BMI 25 Reference BSA: —
BMI 25 Reference Weight: —
BMI 25 Reference Weight: —
TBW-based BSA may overestimate indexed pump-flow targets in obesity. Use the calculated flow as a starting reference and individualize it using temperature, DO₂i, hemoglobin or hematocrit, SvO₂, lactate, arterial pressure, patient condition, and institutional protocol. Do not reduce flow by a fixed rule.
Methodology & clinical notes
This calculator estimates body surface area and BSA-indexed CPB flow references for perfusion planning. Formula details and evidence notes are summarized in the extended section below.
- Default formula: Mosteller is used as the primary adult default because it is simple and reproducible.
- Comparison formulas: Du Bois, Haycock, and Boyd are available to compare formula behavior in selected patients.
- Flow sheet: Blood flow rows are BSA-indexed adult CPB references by cardiac index, with mL/kg/min shown only as a secondary weight-indexed conversion.
- Clinical interpretation: Use these values as reference guidance and interpret them with patient status, institutional practice, and perfusion adequacy markers.
Worked example: BSA and CPB pump flow
For a patient who is 170 cm tall and weighs 70 kg, the Mosteller formula gives an internal BSA of approximately 1.8181 m², displayed as 1.82 m². At a cardiac index of 2.4 L/min/m², the corresponding BSA-indexed pump flow is displayed as 4.36 L/min.
Step 1 — Calculate BSA
BSA = √((height × weight) ÷ 3600)
BSA = √((170 × 70) ÷ 3600)
BSA = √3.3056
BSA = 1.8181... m²
Displayed BSA = 1.82 m²
Step 2 — Calculate BSA-indexed pump flow
Pump flow = BSA × cardiac index
Pump flow = 1.8181... × 2.4
Pump flow = 4.3635... L/min
Displayed pump flow = 4.36 L/min
Step 3 — Show the weight-indexed reference
mL/kg/min = (pump flow × 1000) ÷ weight
mL/kg/min = (4.3635... × 1000) ÷ 70
mL/kg/min = 62.3...
Displayed reference = 62 mL/kg/min
Precision note: The calculator displays BSA to two decimal places but calculates the flow table from the unrounded internal BSA. For this reason, multiplying the displayed 1.82 m² by 2.4 may give 4.37 L/min, while the calculator correctly displays 4.36 L/min from the full-precision BSA.
This example demonstrates the calculation only. BSA-indexed flow is a planning reference and should be interpreted with temperature, hemoglobin or hematocrit, venous oxygen saturation, lactate, perfusion pressure, oxygen-delivery assessment, patient condition, and institutional protocol.
Extended clinical notes & evidence
Additional interpretation for BSA formula behavior, CPB flow indexing context, and obesity-specific considerations.
BSA formula notes
Du Bois & Du Bois
Historically important and widely cited as an adult comparison formula.
BSA = 0.007184 × H0.725 × W0.425
Why it matters: helpful reference when comparing formula behavior.
Haycock
Often considered in pediatric body-size estimation and smaller body sizes.
BSA = 0.024265 × H0.3964 × W0.5378
Typical use: pediatric-leaning comparisons in selected patients.
Boyd
Broader body-size modeling, though less common in routine practice.
BSA = 0.0003207 × H(cm)0.3 × W(g)(0.7285 − 0.0188 × log10(W(g)))
Unit note: Boyd requires height in centimeters and weight converted to grams.
Why it matters: offers an additional reference in non-standard body habitus.
Clinical context in CPB
BSA indexing helps normalize adult CPB pump flow references across different body sizes. The primary flow framework is BSA × CI; mL/kg/min is shown only as a weight-indexed reference conversion for users who want to view the same BSA-based flow by body weight.
Cardiac Index (CI) = Pump Flow (L/min) ÷ BSA (m²)
Pump Flow (L/min) = BSA (m²) × CI (L/min/m²)
mL/kg/min = [Pump Flow (L/min) × 1000] ÷ weight (kg)
Use the calculated BSA with pump flow in the DO₂i Calculator to estimate indexed oxygen delivery during CPB.
- BSA-based indexing can help standardize flow interpretation across different patient sizes.
- mL/kg/min should not be used alone to set an adult CPB target, especially when total body weight may overstate metabolic demand.
- Lower temperatures reduce metabolic demand, so acceptable indexed flow may vary with temperature.
- Indexed flow is a starting point, not a complete adequacy measure.
- Temperature, hemoglobin/hematocrit, SvO₂, lactate, arterial pressure, oxygen delivery adequacy, and overall clinical context should also be assessed.
Moderate hypothermia may allow lower indexed flow than near-normothermic bypass.
Higher indexed flow targets are commonly used closer to normothermia.
Exact targets should follow local protocol and patient context.
Obesity considerations: TBW-based BSA vs BMI 25 reference
In obesity, TBW-based BSA may overestimate indexed flow targets. The BMI 25 reference provides a comparison size, not an automatic flow target.
Clinical studies have evaluated ideal-weight-derived flow in patients with obesity and body-composition-based individualization beyond BSA. They support using the comparison alongside physiologic monitoring, but do not establish BMI 25 flow as a universal target.
| Item | TBW-based | BMI 25 reference |
|---|---|---|
| BSA estimate | May overestimate demand | Comparison reference only |
| Indexed flow target | May trend higher | Not an automatic target |
| Perfusion assessment | Needs SvO₂, lactate, temp context | Still needs clinical correlation |
- TBW-based BSA can still be used as a starting point.
- Do not reduce flow by a fixed rule based on BMI or the BMI 25 reference.
- SvO₂, lactate, temperature, and overall clinical context should guide real-time interpretation.
- Follow local protocol for perfusion management.
BSA and CPB flow FAQ
What is BSA used for during cardiopulmonary bypass?
Body surface area is used to index pump flow and other physiologic references to patient size. During CPB, a selected cardiac index can be multiplied by BSA to estimate a reference pump flow, but the result still requires clinical interpretation.
How is BSA calculated with the Mosteller formula?
The Mosteller formula is BSA (m²) = √[(height in cm × weight in kg) ÷ 3600]. For a height of 170 cm and weight of 70 kg, the unrounded result is approximately 1.8181 m² and the calculator displays 1.82 m².
How do you calculate CPB pump flow from BSA and cardiac index?
Pump flow (L/min) = BSA (m²) × cardiac index (L/min/m²). This calculator uses the unrounded internal BSA for the flow table and displays pump flow to two decimal places.
Does BSA alone determine adequate CPB flow?
No. BSA-indexed flow is a starting reference, not a complete adequacy measure. Interpretation should also consider temperature, hemoglobin or hematocrit, venous oxygen saturation, lactate, arterial pressure, oxygen delivery, patient condition, and institutional protocol.
Evidence: Alston et al. 2006Should a patient with obesity automatically receive the full TBW-based BSA flow?
Not automatically, and flow should not be reduced by a fixed rule either. Total-body-weight BSA increases as adipose mass increases, but adipose tissue has substantially lower resting oxygen use per kilogram than highly metabolic organs and lean tissue. A TBW-based target can therefore overstate metabolic flow demand in some patients with obesity. Use the TBW table as a starting reference, use the BMI 25 reference flow only as a comparison aid, and individualize flow using temperature, indexed oxygen delivery, hemoglobin or hematocrit, SvO₂, lactate, arterial pressure, and institutional protocol.
Evidence: Santambrogio et al. 2009How do body fat, blood volume, and metabolic demand relate?
The mL/kg/min column is a flow conversion, not a blood-volume calculation. Blood volume does not rise in direct proportion to every kilogram in obesity, and adipose tissue contributes less resting oxygen demand than the same mass of organ-rich lean tissue. Neither total weight nor a BMI 25 reference size should be used alone to judge adequate CPB perfusion.
Can this flow table be used for pediatric or neonatal CPB?
No. A BSA formula can estimate surface area at smaller body sizes, but this page's CI 1.0–3.0 flow table is adult CPB guidance. Pediatric and neonatal patients have age- and size-dependent oxygen consumption and flow requirements; use a dedicated pediatric perfusion protocol rather than this adult table.
Which weight should be used when edema or fluid overload is present?
Measured weight can be inflated by ascites, pleural fluid, or generalized edema and may overestimate BSA-based flow. When clinically appropriate, use a documented pre-illness or dry-weight reference according to the institutional protocol rather than substituting an estimated weight without clinical review.
What is the difference between cardiac output and cardiac index?
Cardiac output is total blood flow in liters per minute. Cardiac index divides cardiac output by BSA and is expressed in L/min/m²; this calculator reverses that relationship by multiplying the selected cardiac index by BSA to display a pump-flow reference.
Selected references
Formula references
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317:1098.
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863.
- 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;93:62.
- Boyd E. The Growth of the Surface Area of the Human Body.
Body composition and blood-volume references
- Gallagher D, et al. Organ-tissue mass measurement allows modeling of REE and metabolically active tissue mass. Am J Physiol. 1998;275:E249–E258. PubMed
- Lemmens HJM, Bernstein DP, Brodsky JB. Estimating blood volume in obese and morbidly obese patients. Obes Surg. 2006;16:773–776. PubMed
CPB flow individualization references
- Alston RP, Anderson A, Sanger K. Is body surface area still the best way to determine pump flow rate during cardiopulmonary bypass? Perfusion. 2006;21(3):139–145. PubMed
- Santambrogio L, Leva C, Musazzi G, Bruno P, et al. Determination of pump flow rate during cardiopulmonary bypass in obese patients avoiding hemodilution. J Card Surg. 2009;24(3):245–249. PubMed
- Thomassen SA, Larsson A, Andreasen JJ, Bundgaard W. Should blood flow during cardiopulmonary bypass be individualized more than to body surface area? Perfusion. 2011;26:45–50. PubMed