Body Surface Area Calculator
Use this body surface area calculator to calculate your BSA from your height and weight using the Mosteller formula.
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Kevin Cyr, MD
Kevin Cyr, MD, is a board-certified internal medicine physician who trained at Stanford University School of Medicine and completed residency at Cedars-Sinai Medical Center.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Body Surface Area (BSA) Is Calculated
Your body surface area isn't something you'd ever measure with a tape. It's calculated, and it exists almost entirely for other people's use, pharmacists, oncologists, and burn units, rather than for tracking your own fitness. BSA translates your height and weight into a single number, in square meters, that several medical calculations rely on instead of weight alone.
What BSA Measures
Unlike the ratio-based calculators elsewhere on this site, BSA isn't a health risk indicator at all. It's a scaling number used to make other calculations proportional to body size rather than just body weight, most often medication doses.
The Formula
This calculator uses the Mosteller formula², the simpler and more common version in modern clinical use:
BSA (m²) = √( [height (cm) × weight (kg)] ÷ 3600 )
An older, more complex alternative is the original 1916 Du Bois formula¹, which uses fractional exponents rather than a square root:
Du Bois formula: BSA (m²) = 0.007184 × height (cm)^0.725 × weight (kg)^0.425
The two formulas typically land within a percent or two of each other for an average adult¹.
How This Calculator Computes Your Result
Whatever units you enter, height and weight are converted to centimeters and kilograms internally before the Mosteller formula runs, since that's the unit pairing the formula was built around. Your result always displays in square meters, matching clinical convention regardless of your input units.
Where BSA Is Used
BSA shows up most in chemotherapy dosing, burn assessments, and cardiac measurements, since these all scale better with body surface than with weight alone. A study comparing several BSA formulas against directly measured surface area confirmed that both Du Bois and Mosteller stay reasonably accurate for adults, while formulas like Haycock's work better for infants and young children³.
A Note on Accuracy
This number is only as good as the formula behind it, and formulas are approximations built from population averages, not your own measured surface area. In any setting where precision genuinely matters, calculating a chemotherapy dose is the clearest example, a clinician is working from validated protocols, not a public calculator.
Frequently Asked Questions
What is body surface area used for?
Mostly medication dosing, especially chemotherapy, along with burn assessment and certain cardiac measurements, since these scale better with skin surface area than with weight alone.
Which formula does this calculator use?
The Mosteller formula², chosen because it's simpler to compute while producing nearly the same results as the original Du Bois equation for most adults¹.
How accurate is this calculator?
Reasonably accurate for most adults, and Mosteller is one of the most common BSA formulas used in clinical settings¹. For infants and young children, formulas like Haycock's tend to perform better³
Do I need this for everyday fitness tracking?
Not typically. BSA is a clinical measurement, so weight, body fat percentage, or waist circumference are more useful for general fitness tracking.
Sources
A Formula to Estimate the Approximate Surface Area if Height and Weight Be Known, Du Bois & Du Bois, 1916
Simplified Calculation of Body-Surface Area, Mosteller, 1987
Geometric Method for Measuring Body Surface Area, Haycock et al., 1978
Body Surface Area Calculator
Use this body surface area calculator to calculate your BSA from your height and weight using the Mosteller formula.
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Kevin Cyr, MD
Kevin Cyr, MD, is a board-certified internal medicine physician who trained at Stanford University School of Medicine and completed residency at Cedars-Sinai Medical Center.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Body Surface Area (BSA) Is Calculated
Your body surface area isn't something you'd ever measure with a tape. It's calculated, and it exists almost entirely for other people's use, pharmacists, oncologists, and burn units, rather than for tracking your own fitness. BSA translates your height and weight into a single number, in square meters, that several medical calculations rely on instead of weight alone.
What BSA Measures
Unlike the ratio-based calculators elsewhere on this site, BSA isn't a health risk indicator at all. It's a scaling number used to make other calculations proportional to body size rather than just body weight, most often medication doses.
The Formula
This calculator uses the Mosteller formula², the simpler and more common version in modern clinical use:
BSA (m²) = √( [height (cm) × weight (kg)] ÷ 3600 )
An older, more complex alternative is the original 1916 Du Bois formula¹, which uses fractional exponents rather than a square root:
Du Bois formula: BSA (m²) = 0.007184 × height (cm)^0.725 × weight (kg)^0.425
The two formulas typically land within a percent or two of each other for an average adult¹.
How This Calculator Computes Your Result
Whatever units you enter, height and weight are converted to centimeters and kilograms internally before the Mosteller formula runs, since that's the unit pairing the formula was built around. Your result always displays in square meters, matching clinical convention regardless of your input units.
Where BSA Is Used
BSA shows up most in chemotherapy dosing, burn assessments, and cardiac measurements, since these all scale better with body surface than with weight alone. A study comparing several BSA formulas against directly measured surface area confirmed that both Du Bois and Mosteller stay reasonably accurate for adults, while formulas like Haycock's work better for infants and young children³.
A Note on Accuracy
This number is only as good as the formula behind it, and formulas are approximations built from population averages, not your own measured surface area. In any setting where precision genuinely matters, calculating a chemotherapy dose is the clearest example, a clinician is working from validated protocols, not a public calculator.
Frequently Asked Questions
What is body surface area used for?
Mostly medication dosing, especially chemotherapy, along with burn assessment and certain cardiac measurements, since these scale better with skin surface area than with weight alone.
Which formula does this calculator use?
The Mosteller formula², chosen because it's simpler to compute while producing nearly the same results as the original Du Bois equation for most adults¹.
How accurate is this calculator?
Reasonably accurate for most adults, and Mosteller is one of the most common BSA formulas used in clinical settings¹. For infants and young children, formulas like Haycock's tend to perform better³
Do I need this for everyday fitness tracking?
Not typically. BSA is a clinical measurement, so weight, body fat percentage, or waist circumference are more useful for general fitness tracking.
Sources
A Formula to Estimate the Approximate Surface Area if Height and Weight Be Known, Du Bois & Du Bois, 1916
Simplified Calculation of Body-Surface Area, Mosteller, 1987
Geometric Method for Measuring Body Surface Area, Haycock et al., 1978
Body Surface Area Calculator
Use this body surface area calculator to calculate your BSA from your height and weight using the Mosteller formula.
Calculated instantly in your browser — nothing is sent to or stored on our servers.
Kevin Cyr, MD
Kevin Cyr, MD, is a board-certified internal medicine physician who trained at Stanford University School of Medicine and completed residency at Cedars-Sinai Medical Center.
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Body Surface Area (BSA) Is Calculated
Your body surface area isn't something you'd ever measure with a tape. It's calculated, and it exists almost entirely for other people's use, pharmacists, oncologists, and burn units, rather than for tracking your own fitness. BSA translates your height and weight into a single number, in square meters, that several medical calculations rely on instead of weight alone.
What BSA Measures
Unlike the ratio-based calculators elsewhere on this site, BSA isn't a health risk indicator at all. It's a scaling number used to make other calculations proportional to body size rather than just body weight, most often medication doses.
The Formula
This calculator uses the Mosteller formula², the simpler and more common version in modern clinical use:
BSA (m²) = √( [height (cm) × weight (kg)] ÷ 3600 )
An older, more complex alternative is the original 1916 Du Bois formula¹, which uses fractional exponents rather than a square root:
Du Bois formula: BSA (m²) = 0.007184 × height (cm)^0.725 × weight (kg)^0.425
The two formulas typically land within a percent or two of each other for an average adult¹.
How This Calculator Computes Your Result
Whatever units you enter, height and weight are converted to centimeters and kilograms internally before the Mosteller formula runs, since that's the unit pairing the formula was built around. Your result always displays in square meters, matching clinical convention regardless of your input units.
Where BSA Is Used
BSA shows up most in chemotherapy dosing, burn assessments, and cardiac measurements, since these all scale better with body surface than with weight alone. A study comparing several BSA formulas against directly measured surface area confirmed that both Du Bois and Mosteller stay reasonably accurate for adults, while formulas like Haycock's work better for infants and young children³.
A Note on Accuracy
This number is only as good as the formula behind it, and formulas are approximations built from population averages, not your own measured surface area. In any setting where precision genuinely matters, calculating a chemotherapy dose is the clearest example, a clinician is working from validated protocols, not a public calculator.
Frequently Asked Questions
What is body surface area used for?
Mostly medication dosing, especially chemotherapy, along with burn assessment and certain cardiac measurements, since these scale better with skin surface area than with weight alone.
Which formula does this calculator use?
The Mosteller formula², chosen because it's simpler to compute while producing nearly the same results as the original Du Bois equation for most adults¹.
How accurate is this calculator?
Reasonably accurate for most adults, and Mosteller is one of the most common BSA formulas used in clinical settings¹. For infants and young children, formulas like Haycock's tend to perform better³
Do I need this for everyday fitness tracking?
Not typically. BSA is a clinical measurement, so weight, body fat percentage, or waist circumference are more useful for general fitness tracking.
Sources
A Formula to Estimate the Approximate Surface Area if Height and Weight Be Known, Du Bois & Du Bois, 1916
Simplified Calculation of Body-Surface Area, Mosteller, 1987
Geometric Method for Measuring Body Surface Area, Haycock et al., 1978