Clinical body-weight calculation
Enter height and actual weight to calculate Devine IBW, actual weight as a percentage of IBW, and the Devine + 0.4 adjusted body weight when that method is specifically required by the governing source.
Sex used by the Devine equation
Select the male or female Devine IBW equation required by the relevant reference.
Height entry
Choose centimetres or feet + inches.
The AdjBW calculator uses the Devine IBW equation and does not calculate below 152.4 cm (5 feet).
Actual weight unit
Enter the patient's actual body weight in kg or lb.
Enter the measured actual body weight.
Use AdjBW only when it is specifically required
Simple answer
When the governing medicine reference or protocol specifically requires the Devine + 0.4 method, calculate IBW first, then add 40% of the excess of actual weight above IBW.
This is a calculation method only. Use AdjBW only when the relevant medicine reference or protocol specifically requires it.
A Devine-based 0.4 adjusted body weight: Devine IBW plus 40% of the difference between actual weight and IBW. Other AdjBW calculators can differ if they use another IBW equation or adjustment factor.
MedMaths uses AdjBW for adjusted body weight because ABW is ambiguous and can mean actual body weight in clinical sources. Check the abbreviation used by the medicine reference or protocol.
Current protocols do not use one universal switch point. ZEMDRI prescribing information uses adjusted body weight when total body weight is at least 25% above IBW and explicitly defines the 0.4 equation, while UCSF uses >120% of IBW for multiple antimicrobials. The calculator shows the arithmetic context; the governing source decides whether AdjBW applies.
Clinical use and safety
The arithmetic can be correct while the clinical decision is still wrong. These boundaries show what the calculator can and cannot establish.
Formula logic and known-value examples are checked as part of the MedMaths review process.
See how MedMaths checks calculator methods →Review the Devine + 0.4 method, formula provenance, two worked examples, common mistakes and focused FAQs.
In simple words
Calculate how much actual weight is above IBW, take 40% of that difference, then add it to IBW.
Devine IBW used as the base
Male: IBW = 50 + 2.3 × (height in inches − 60)
Female: IBW = 45.5 + 2.3 × (height in inches − 60)
This calculator does not extrapolate the Devine equation below 152.4 cm (5 feet).
Adjusted body weight is not one universally standardised number. This implementation uses Devine IBW as the base and the common 0.4 adjustment convention.
The 0.4 factor should not be credited to a single verified inventor. Traynor and colleagues described 40% of excess weight as an existing approach in 1995 and derived a factor of 0.43 in their aminoglycoside dataset. Later studies evaluated 0.4 in specific clinical settings.
If another calculator uses Robinson IBW, another correction factor or a different application threshold, it is calculating a different AdjBW method.
These examples teach the arithmetic only. They do not tell you which body weight should be used for a specific medicine or patient.
Height 175 cm, actual weight 120 kg.
Answer: 90.3 kg
Height 5 ft 6 in, actual weight 220 lb.
Answer: 75.5 kg
A calculated AdjBW does not mean it is the correct weight for the medicine. The applicable source must name the method or threshold.
Some protocols use >120% IBW, but others use BMI-based or medicine-specific criteria. Follow the source you are using.
The formula uses 40% of the difference between actual weight and IBW, not 40% of the whole actual weight.
Devine vs Robinson IBW and different correction factors can produce different adjusted weights.
ABW can mean actual body weight in some sources. MedMaths uses AdjBW for adjusted body weight.
Actual weight and IBW must use the same units before subtraction. MedMaths converts lb to kg internally.
The percentage shown is rounded for readability. Use the exact comparison rule in the governing source rather than deciding from the rounded display alone.
The calculator should not choose between actual, ideal and adjusted body weight for you. For the deeper renal-function context, including why weight selection changes Cockcroft-Gault creatinine clearance, use the dedicated Guide.
This page combines Devine ideal body weight with the commonly used 0.4 adjusted-weight convention. MedMaths does not attribute the 0.4 method to a single verified creator. Published studies have evaluated this convention in specific settings, including aminoglycoside dosing and Cockcroft-Gault creatinine-clearance estimation; it is not a universal dosing-weight rule.
Supporting references
Continue calculating
Use these calculators when a medicine reference requires a specific dosing weight.
Calculate adult Devine ideal body weight in cm or feet and inches, with optional Robinson and Miller comparison estimates.
Open calculatorCalculate body surface area from metric or imperial height and weight using four published formulas.
Open calculatorCalculate adult Cockcroft-Gault CrCl when a medicine label, protocol or exam specifically requires this method.
Open calculatorCalculate mg/kg per-dose or per-day orders using kg or lb, divided doses, and liquid concentration.
Open calculatorOpen the prescribing information, regulatory guidance and primary publications supporting the Devine + 0.4 method and its source-specific use.
Medicine-specific label example — ZEMDRI (plazomicin)
ZEMDRI prescribing information uses adjusted body weight when total body weight is at least 25% above IBW and explicitly defines: AdjBW = IBW + 0.4 × (TBW − IBW). This is a medicine-specific example, not a universal switch point.
DailyMed — ZEMDRI professional labelingRenal-function guidance
U.S. Food and Drug Administration. Pharmacokinetics in Patients with Impaired Renal Function — Study Design, Data Analysis, and Impact on Dosing. March 2024. The guidance notes that alternative weight metrics such as IBW or adjusted body weight can improve Cockcroft-Gault estimation in overweight or obese individuals.
FDA final guidanceDevine IBW publication
McCarron MM, Devine BJ. Clinical Pharmacy: Case Studies: Case Number 25 Gentamicin Therapy. Drug Intelligence & Clinical Pharmacy. 1974;8(11):650–655. DOI: 10.1177/106002807400801104.
Primary correction-factor evidence
Traynor AM, Nafziger AN, Bertino JS Jr. Aminoglycoside dosing weight correction factors for patients of various body sizes. Antimicrob Agents Chemother. 1995;39(2):545–548. PMID: 7726530. The paper describes the prior 40% approach and derived a factor of approximately 0.43 in its overweight population.
PubMed PMID 7726530Adjusted body weight in Cockcroft-Gault estimation
Winter MA, Guhr KN, Berg GM. Impact of various body weights and serum creatinine concentrations on the bias and accuracy of the Cockcroft-Gault equation. Pharmacotherapy. 2012;32(7):604–612. PMID: 22576791.
PubMed PMID 22576791Current institutional example — >120% of IBW
UCSF Infectious Diseases Management Program. Dosing Weights. Multiple antimicrobial entries use adjusted body weight when total body weight is greater than 120% of ideal body weight.
UCSF dosing weightsCurrent obesity-dosing review
Contemporary antimicrobial obesity-dosing literature describes adjusted body weight generally as IBW + C × (TBW − IBW), with the correction factor depending on the drug or protocol rather than being universally fixed at 0.4.
Peer-reviewed reviewBMI-based example from NHS guidance
NHS Lothian / Right Decisions. Daptomycin guidance. An example of a different, BMI-based trigger for adjusted body weight.
NHS Lothian daptomycin guidance