Calculate adjusted body weight (AdjBW) from ideal body weight, actual body weight, and a correction factor (default 0.40). AdjBW is a calculated body-size descriptor — not a medication dose, target weight, or diagnosis.
Last updated: September 2026 · Written by the CalculatorSearch team · Reviewed by [Add a genuine, credentialed clinician or pharmacist reviewer before publishing — do not publish this placeholder as a real reviewer]
This calculator is for informational and mathematical purposes. Adjusted body weight is a specialized body-size descriptor and is not, by itself, a medication dose or a universal dosing weight. Medication dosing should follow the drug-specific prescribing information and guidance of a qualified healthcare professional.
cm
kg
ftin
lb
Figures use the Devine ideal-body-weight formula and are calculated for adults. This calculator does not provide medication doses and is not intended for pediatric or pregnancy-related dosing decisions.
What is adjusted body weight?
Adjusted body weight (AdjBW) is a calculated body-size measure that combines ideal body weight with a specified fraction of the difference between actual and ideal body weight. A commonly used equation is AdjBW = IBW + 0.4 × (TBW − IBW). The appropriate correction factor depends on the clinical context.
What formula does this calculator use?
Ideal body weight is calculated with the Devine formula. Adjusted body weight is then AdjBW = IBW + CF × (TBW − IBW), with a default correction factor of 0.40 and 0.25/0.30/custom also selectable.
Can AdjBW tell me my medication dose?
No. An adjusted body weight result alone is not enough to determine a safe medication dose. Dosing decisions depend on the specific drug, indication, renal and hepatic function, and the applicable prescribing protocol — determined by a qualified healthcare professional.
Key Facts
AdjBW is calculated, not directly measured.
It uses actual body weight and ideal body weight.
A common correction factor is 0.40.
The correction factor is not universal — it varies by protocol.
AdjBW is not the same as lean body weight.
AdjBW is not the same as fat-free mass.
AdjBW is sometimes used as a clinical dosing-weight descriptor.
Drug-specific protocols may use different body-size scalars entirely.
What Is Adjusted Body Weight?
Adjusted body weight is a calculated body-size descriptor that modifies ideal body weight by adding a fraction of the excess actual body weight above it. It's defined mathematically as:
AdjBW = IBW + CF × (TBW − IBW)
where CF is the correction factor — commonly 0.40 in the example this calculator defaults to, though other values appear in different clinical contexts. This is not presented as "the universal adjusted body weight formula" — it's one widely referenced convention among several.
Why Is Adjusted Body Weight Used?
In obesity, actual body weight does not always have a linear relationship with how a drug distributes through and clears from the body. For selected drugs, clinicians may use an adjusted weight descriptor rather than simply applying a per-kilogram calculation to total body weight. However, drug behavior differs substantially between medications, so there is no universal rule that adjusted body weight should be used for all — or even most — medications. Clinical literature consistently emphasizes that the appropriate body-weight descriptor depends on the specific drug and context.
Adjusted Body Weight Formula
AdjBW = IBW + CF × (TBW − IBW)
Where:
TBW — Total (actual) body weight: your measured, current scale weight.
IBW — Ideal body weight: a formula-based reference estimate (see below).
CF — Correction factor: the fraction of excess weight added back to IBW. Default 0.40.
Behavior check: if TBW = IBW, AdjBW = IBW. If TBW > IBW and 0 < CF < 1, then IBW < AdjBW < TBW — the result sits between the two, moving toward TBW as CF increases, but never reaching TBW while CF is below 1.
Ideal Body Weight Formula Used
Because AdjBW requires IBW as an input, this calculator first computes ideal body weight using the Devine formula:
Men: IBW = 50 kg + 2.3 kg × (inches over 5 ft)
Women: IBW = 45.5 kg + 2.3 kg × (inches over 5 ft)
For heights at or below 5 ft, this calculator extends the formula consistently rather than blocking the calculation — "inches over 5 ft" becomes zero or negative and is applied the same way arithmetically. This is a documented implementation choice, not a claim that the Devine formula was validated across all heights.
IBW here is an intermediate value used only to compute AdjBW. It is not presented as a universally ideal weight, a medical target, a guaranteed healthy weight, or any individual's personal optimal weight. For a broader comparison of IBW formulas (Devine, Robinson, Miller, Hamwi), see the Ideal Weight Calculator — this AdjBW calculator uses Devine specifically because that's the IBW equation most commonly paired with the AdjBW methodology in the literature.
What Does the 0.4 Correction Factor Mean?
A correction factor of 0.4 means the equation adds 40% of the difference between total body weight and ideal body weight back onto the ideal body weight. For example, with TBW = 120 kg and IBW = 70 kg: excess weight is 50 kg, 40% of that is 20 kg, so AdjBW = 70 + 20 = 90 kg. This is a mathematical explanation only — it is not a dosing recommendation.
Why 0.4?
The 0.4 factor is a commonly used convention in some adjusted-weight calculations, particularly certain aminoglycoside dosing contexts described in clinical literature. It should not be treated as a universal biological constant — other literature and other drug-specific protocols use different correction factors in different settings.
Why Do Some Sources Use 0.25 Instead of 0.4?
Different drugs and clinical protocols may specify different correction factors — published references describe adjusted body weight using factors ranging from approximately 0.25 to 0.40 depending on context. 0.25 is not simply a lower-precision version of 0.40; the two represent different clinical conventions. This calculator does not tell you which factor applies to a specific medication — that determination comes from the applicable drug-specific or institutional protocol.
If you select a non-default correction factor, remember: different clinical protocols may specify different correction factors — use the factor specified by the applicable drug-specific or institutional protocol, not the one that seems most familiar.
Custom Correction Factor
An advanced "Custom…" option is available for cases where a specific protocol names a value outside the common presets. Use a custom correction factor only when it is specified by the applicable clinical protocol or a validated methodology — a custom result is never labeled "recommended" by this calculator.
What Happens If Actual Weight Is Below Ideal Weight?
If TBW is below IBW, the standard equation can still produce a mathematical result, but this should not be assumed to be clinically appropriate. Adjusted body weight is primarily used as a specialized body-size descriptor for people whose actual weight exceeds their calculated ideal weight. If your actual weight is below your calculated ideal weight, the appropriate weight scalar for any specific purpose depends on the applicable clinical protocol — this calculator does not invent a universal rule for that situation, but it will still show the mathematical result with a clear note.
Quick result breakdown
Actual weight (TBW) — what you entered.
Ideal weight (IBW) — calculated with the Devine formula.
Excess weight — TBW minus IBW.
Correction factor — the selected fraction, default 0.40.
Adjusted body weight — IBW plus (correction factor × excess weight).
Worked Examples
Example 1 — Male, 175 cm, 120 kg, CF 0.40
Height: 175 cm → 68.90 in → 8.90 in over 5 ft IBW = 50 + 2.3 × 8.90 = 70.5 kg Excess weight = 120 − 70.5 = 49.5 kg AdjBW = 70.5 + 0.40 × 49.5 = 70.5 + 19.8 = 90.3 kg
Illustrative mathematical example only — not a medical recommendation.
Example 2 — Female, 165 cm, 100 kg, CF 0.40
Height: 165 cm → 64.96 in → 4.96 in over 5 ft IBW = 45.5 + 2.3 × 4.96 = 56.9 kg Excess weight = 100 − 56.9 = 43.1 kg AdjBW = 56.9 + 0.40 × 43.1 = 56.9 + 17.2 = 74.1 kg
Example 3 — Same person as Example 1, different correction factors
IBW = 70.5 kg, Excess = 49.5 kg CF 0.25: AdjBW = 70.5 + 0.25×49.5 = 82.8 kg CF 0.30: AdjBW = 70.5 + 0.30×49.5 = 85.3 kg CF 0.40: AdjBW = 70.5 + 0.40×49.5 = 90.3 kg
The correction factor can materially affect the result — this is not a recommendation to choose one factor over another.
Weight Descriptor Comparison
Several related but distinct body-size measures are often discussed together. This calculator distinguishes them clearly rather than treating them as interchangeable:
Measure
What it means
Actual (total) body weight
Measured, current scale weight
Ideal body weight (IBW)
Formula-based reference estimate from height and sex
Adjusted body weight (AdjBW)
IBW plus a selected fraction of excess weight above IBW
Lean body weight (LBW)
Estimated non-fat component of body mass, via a separate equation
Fat-free mass (FFM)
Body mass excluding fat, a related but distinct body-composition measure
Adjusted Body Weight vs Ideal Body Weight
IBW is calculated from height and sex alone. AdjBW starts from that IBW and adds back a fraction of your actual excess weight, so it also reflects your real body size — AdjBW and IBW are equal only when actual weight equals ideal weight.
Adjusted Body Weight vs Lean Body Weight
AdjBW is a mathematical dosing/body-size descriptor built from IBW and excess weight. LBW is an estimate of lean, non-fat body mass using its own separate equation. Clinical literature distinguishes these descriptors, and they should not be used interchangeably. See the Lean Body Mass Calculator.
Adjusted Body Weight vs Fat-Free Mass
Fat-free mass attempts to represent body mass excluding fat; AdjBW is a dosing/body-size scalar built from height, sex, and excess weight. They answer different questions and are not automatically equivalent.
Adjusted Body Weight vs BMI
BMI = weight / height², a general weight-height screening index. AdjBW uses IBW and a correction factor applied to excess weight — a specialized calculated weight descriptor, not a screening measure. See the BMI Calculator.
Adjusted Body Weight vs Body Surface Area
BSA estimates body surface area in m² from height and weight. AdjBW estimates a body-weight scalar in kg from IBW and excess weight. They're different calculations answering different questions. See the Body Surface Area Calculator.
Adjusted Body Weight vs Healthy Weight
The Healthy Weight Calculator provides an adult BMI-derived reference range. Adjusted body weight is a specialized clinical body-size descriptor used in selected dosing contexts. They are not interchangeable — one is a general screening range, the other a narrow clinical calculation.
Clinical Use and Medication Safety
Can I Use Adjusted Body Weight to Calculate My Medication Dose?
No. An adjusted body weight result alone is not enough to determine a safe medication dose. Actual dosing may depend on the drug, indication, route, actual body weight, ideal body weight, adjusted body weight, renal function, hepatic function, age, clinical condition, pharmacokinetics, therapeutic drug monitoring, maximum and minimum dose limits, and institutional protocol. This calculator does not provide dosing equations for any specific drug.
Adjusted Body Weight and Aminoglycosides
Adjusted-weight calculations have been used in some aminoglycoside dosing approaches described in clinical literature. This page does not provide a gentamicin, tobramycin, or amikacin dose, a mg/kg regimen, a dosing interval, or a loading dose. Drug-specific dosing should follow the current prescribing information and clinical protocol.
Adjusted Body Weight and Vancomycin
Body-size descriptors used for vancomycin dosing vary by protocol and patient circumstances, and current clinical references can recommend different approaches depending on the drug and situation. This page does not provide a vancomycin dose calculator, and AdjBW is not presented as universally the correct scalar for it.
Adjusted Body Weight and Kidney Function
Some creatinine-clearance equations have historically incorporated body-weight choices, but the appropriate weight input can vary by equation and clinical context — AdjBW is not automatically inserted into a GFR or creatinine-clearance calculation here. AdjBW does not measure kidney function; a calculated adjusted weight may be one input in certain renal-function or drug-dosing methods, but this depends entirely on the specific method being used. See the GFR Calculator for kidney-function estimation specifically.
Pediatric Considerations
This calculator uses adult formulas — the Devine IBW equation and standard AdjBW methodology — which should not automatically be applied to children. Pediatric pharmacokinetics differ meaningfully from adults. This calculator does not encourage pediatric medication dosing; for children, use pediatric-specific clinical protocols and qualified healthcare guidance. See the Child BMI Calculator for pediatric BMI-for-age instead.
Pregnancy Considerations
This calculator does not provide pregnancy-specific adjusted-weight guidance. Pregnancy changes body composition and pharmacokinetics, so generic adult AdjBW formulas should not be used to make medication decisions during pregnancy without appropriate clinical guidance.
Extreme Body Size
Formula performance and clinical usefulness may vary at extremes of obesity, height, body composition, and illness. No universal accuracy threshold is claimed for any body size.
How Accurate Is an Adjusted Body Weight Calculator?
The arithmetic can be calculated precisely — this calculator does not round intermediate values, only the final displayed figures. But the clinical meaning of the resulting number is context-dependent. This is a critical distinction: calculation precision does not equal clinical validity for every use. A calculator may compute 89.7 kg with mathematical precision, but that does not mean 89.7 kg is the correct dosing weight for every medication, patient, or situation.
Is Adjusted Body Weight Always the Best Weight to Use?
No. Different medications may use actual body weight, ideal body weight, adjusted body weight, lean body weight, fat-free mass, body surface area, or full pharmacokinetic models. The correct approach is drug- and protocol-specific, and clinical references consistently emphasize this variability. There is no universal dosing weight, and clinical protocols vary — drug-specific guidance always takes priority over any single calculated number on this page.
How to Use the Calculator
Enter your sex/reference category.
Enter your height.
Enter your actual body weight.
Select your unit system.
Confirm the Devine IBW methodology is appropriate for your purpose.
Select a correction factor if a specific protocol requires one other than 0.40.
Select Calculate AdjBW.
Review total body weight, ideal body weight, excess weight, and adjusted body weight.
Read the methodology and limitations above before using the result for anything beyond general information.
Adjusted body weight (AdjBW) is a calculated body-size measure that combines ideal body weight with a specified fraction of the difference between actual and ideal body weight. A commonly used equation is AdjBW = IBW + 0.4 × (TBW − IBW). The appropriate correction factor depends on the clinical context.
What is the adjusted body weight formula?
AdjBW = IBW + CF × (TBW − IBW), where IBW is ideal body weight, TBW is total (actual) body weight, and CF is a correction factor — commonly 0.40, though some contexts use 0.25 or 0.30.
What does AdjBW stand for?
AdjBW stands for Adjusted Body Weight.
How do you calculate adjusted body weight?
First calculate ideal body weight (this calculator uses the Devine formula), then add a selected fraction (the correction factor, commonly 0.40) of the difference between actual and ideal body weight.
What is the 0.4 correction factor?
The 0.4 correction factor means the equation adds 40% of the difference between total body weight and ideal body weight to the ideal body weight. It's a commonly used convention in some adjusted-weight calculations, not a universal biological constant.
Why is 0.4 used?
A correction factor of 0.4 is widely referenced in some clinical dosing contexts, particularly certain aminoglycoside-related calculations, but it is not a universal rule for every drug or protocol.
Can adjusted body weight use a 0.25 factor?
Yes. Some references and protocols use a correction factor of 0.25 (or 0.30) instead of 0.40. This calculator lets you select among common factors, but the applicable clinical protocol determines which one is correct for a given use.
Which correction factor should I use?
This calculator does not tell you which correction factor to use. The correct factor depends on the specific drug, indication, and institutional or clinical protocol — use the factor specified by that protocol.
What is ideal body weight?
Ideal body weight (IBW) is a formula-based reference weight estimate, calculated here using the Devine formula from height and sex. It's an intermediate mathematical input for adjusted body weight, not a universally healthy or ideal target.
What is total body weight?
Total body weight (TBW) is the person's actual, measured scale weight — the weight you enter into the calculator.
What is the difference between actual and adjusted body weight?
Actual (total) body weight is your measured scale weight. Adjusted body weight is a calculated value that starts from ideal body weight and adds a fraction of the excess above it — it's typically lower than actual weight when actual weight exceeds ideal weight.
What is the difference between adjusted and ideal body weight?
Ideal body weight is a formula-based reference estimate from height and sex alone. Adjusted body weight starts from that IBW and adds a fraction of the difference between actual and ideal weight, so it also reflects the person's actual body size.
What is the difference between adjusted body weight and lean body weight?
Adjusted body weight is a mathematical dosing/body-size descriptor based on ideal body weight and excess weight. Lean body weight is a separate estimate of the body's non-fat mass, calculated with a different equation. They are not interchangeable and can produce different numbers.
Is adjusted body weight the same as fat-free mass?
No. Fat-free mass attempts to estimate body mass excluding fat, while adjusted body weight is a calculated scalar based on ideal body weight and a correction factor. They answer different questions.
Why is adjusted body weight used in obesity?
In obesity, actual body weight doesn't always relate proportionally to how some drugs distribute and clear from the body. For selected drugs, clinicians may use an adjusted weight descriptor instead of simply applying actual weight — but this varies by drug, so it isn't a universal rule.
Is adjusted body weight used for medication dosing?
Adjusted body weight is used as one possible body-size descriptor in some medication dosing protocols, but which weight scalar to use depends on the specific drug and clinical context.
Can I calculate my medication dose using AdjBW?
No. An adjusted body weight result alone is not enough to determine a safe medication dose. Dosing depends on the drug, indication, route, renal and hepatic function, age, clinical status, and the applicable prescribing protocol — always determined by a qualified healthcare professional.
Is adjusted body weight used for aminoglycosides?
Adjusted body weight has been used in some aminoglycoside dosing approaches described in clinical literature, but specific dosing (such as a gentamicin or tobramycin regimen) should follow current prescribing information and clinical protocol, not this calculator.
Is adjusted body weight used for vancomycin?
Body-size descriptors used for vancomycin dosing vary by protocol and patient circumstances, and current clinical guidance can differ depending on the situation. This page does not provide a vancomycin dosing calculation.
Is adjusted body weight used in kidney calculations?
Some creatinine-clearance and renal-dosing calculations have historically incorporated body-weight choices, and adjusted body weight is sometimes one option, but the appropriate weight input varies by equation and clinical context. AdjBW itself does not measure kidney function.
Can children use an adjusted body weight calculator?
This calculator uses adult formulas (Devine IBW and standard adjusted-weight methodology) and should not automatically be applied to children. Pediatric pharmacokinetics differ from adults — use pediatric-specific clinical protocols and qualified healthcare guidance instead.
Can adjusted body weight be used during pregnancy?
Pregnancy changes body composition and pharmacokinetics in ways generic adult adjusted-weight formulas don't account for. Medication decisions during pregnancy should follow appropriate clinical guidance rather than this calculator's result.
How accurate is adjusted body weight?
The arithmetic can be calculated precisely, but the clinical meaning of the resulting number is context-dependent. A precisely calculated adjusted weight is not automatically the correct dosing weight for every medication or situation.
Is adjusted body weight always better than actual body weight?
No. There is no single body-weight descriptor that is universally best. Different medications may use actual weight, ideal weight, adjusted weight, lean body weight, body surface area, or pharmacokinetic models depending on the drug and context.
Is adjusted body weight always between ideal and actual weight?
When actual weight is above ideal weight and the correction factor is between 0 and 1, adjusted body weight falls between ideal and actual weight. When actual weight is below ideal weight, the result can behave differently and should be interpreted with care.
What happens if actual weight is below ideal weight?
The standard equation can still produce a mathematical result, but adjusted body weight is primarily intended as a descriptor for people whose actual weight exceeds their ideal weight. If actual weight is below ideal weight, the appropriate weight scalar depends on the specific clinical protocol rather than a universal rule.
What formula does this calculator use?
By default, this calculator uses the Devine formula for ideal body weight and AdjBW = IBW + 0.40 × (TBW − IBW) for adjusted body weight, with 0.25 and 0.30 also selectable as alternative correction factors.
Why do different websites give different AdjBW results?
Results can differ because of different ideal-body-weight formulas, different correction factors, or rounding differences between calculators. Always check which IBW formula and correction factor a given tool uses.
Can I use another ideal-weight formula?
This calculator uses the Devine formula specifically for its adjusted-body-weight methodology. For a broader comparison of IBW formulas (Devine, Robinson, Miller, Hamwi), see the Ideal Weight Calculator.
Does adjusted body weight equal lean body mass?
No. Adjusted body weight and lean body mass are calculated with different equations and represent different concepts — one is a dosing/body-size scalar, the other estimates non-fat body mass. They typically produce different numbers for the same person.
Calculation Method & Sources
Default IBW method: Devine formula. Default correction factor: 0.40. Primary formula: AdjBW = IBW + 0.40 × (TBW − IBW). Different clinical protocols can specify different correction factors (commonly 0.25–0.40), and this calculator allows selecting among common values or entering a custom one when a specific protocol requires it. Intermediate values are not rounded; only the final displayed figures are rounded, to one decimal place.
Authoritative references to verify before publishing:
Association of Anaesthetists (or equivalent professional body) guidance discussing AdjBW = IBW + 0.4(TBW − IBW)
Devine BJ — Gentamicin therapy (original IBW formula source, 1974)
Clinical pharmacology literature describing adjusted body weight in aminoglycoside dosing contexts
Obesity pharmacotherapy literature discussing body-size descriptor selection
Current clinical references explaining that correction factors and dosing scalars vary by medication
Author: the CalculatorSearch team. Add a "Reviewed By" credit only once a genuinely qualified clinician or pharmacist has checked this content — do not publish the placeholder byline above as a real reviewer. Content last reviewed: September 2026.
Privacy
This calculator performs its computation in your browser. No account is required, and the tool does not store your height, weight, or any other detail beyond what's needed to display your result on this page.
Medical disclaimer. This calculator is for informational and mathematical purposes. Adjusted body weight is a specialized body-size descriptor and is not, by itself, a medication dose or a universal dosing weight. It should not be interpreted as your ideal weight, your lean body mass, or a target weight of any kind. Medication dosing should follow the drug-specific prescribing information and the guidance of a qualified healthcare professional using the applicable clinical protocol. This calculator is not intended for use in children or during pregnancy without appropriate professional guidance.