Adjusted Body Weight (ABW) Calculator
Estimate ABW from total body weight (TBW) and ideal body weight (IBW, Devine). Includes working out, practice questions, FAQs, and references.
You can type commas (e.g. 1,000). Inputs start blank by default.
Used to estimate IBW (Devine).
IBW differs by sex in the Devine formula.
Educational use only. This calculator provides an estimate and does not replace local policy, clinical judgement, or pharmacist/medical advice.
How it works
Adjusted body weight (ABW) is a dosing weight sometimes used when total body weight (TBW) is above ideal body weight (IBW). The goal is to avoid scaling dose fully with adipose tissue for medications that do not distribute completely into fat.
This calculator estimates IBW using the Devine equation (height + sex), then calculates ABW using a commonly used correction factor (0.4). Always use the dosing weight recommended by your local policy or drug-specific guideline.
Formula
Worked examples
Example 1: Male, height 178 cm, TBW 103 kg
Answer: ABW = 85.11 kg
Example 2: Female, height 165 cm, TBW 95 kg
Answer: ABW = 72.15 kg
Practice questions
Designed for student nurses, junior doctors, and pharmacists who want to verify their steps. Try it first, then reveal the answer and working.
Practice 1: Male, height 180 cm, TBW 120 kg. What is ABW (Devine + 0.4)?
Show answer + working
Answer: ABW ≈ 93.0 kg
Height (in) = 180 ÷ 2.54 = 70.87 in Inches over 60 = 70.87 − 60 = 10.87 IBW (male) = 50 + 2.3×10.87 = 74.99 kg ABW = 74.99 + 0.4×(120 − 74.99) ABW = 74.99 + 0.4×45.01 = 74.99 + 18.00 = 92.99 kg Round to 1–2 decimals depending on your documentation/local preference.
Practice 2: Female, height 165 cm, TBW 95 kg. What is ABW?
Show answer + working
Answer: ABW ≈ 72.15 kg
Height (in) = 165 ÷ 2.54 = 64.96 in Inches over 60 = 64.96 − 60 = 4.96 IBW (female) = 45.5 + 2.3×4.96 = 56.91 kg ABW = 56.91 + 0.4×(95 − 56.91) ABW = 56.91 + 0.4×38.09 = 56.91 + 15.24 = 72.15 kg
Practice 3: Male, height 172 cm, TBW 78 kg. What is ABW?
Show answer + working
Answer: ABW ≈ 71.85 kg
Height (in) = 172 ÷ 2.54 = 67.72 in Inches over 60 = 67.72 − 60 = 7.72 IBW (male) = 50 + 2.3×7.72 = 67.75 kg ABW = 67.75 + 0.4×(78 − 67.75) ABW = 67.75 + 0.4×10.25 = 67.75 + 4.10 = 71.85 kg
Clinical reminder
ABW is not universal. Some drugs dose by TBW, some by IBW, and some require therapeutic drug monitoring (TDM). Always follow your local guideline and consult pharmacy/medical staff when uncertain.
Related calculators
FAQs
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Sources
Core equations & background
Devine BJ (1974) — PubMed record
WebNational Library of Medicine (PubMed)
Original Devine publication reference for IBW estimation used widely in dosing contexts.
Drug Dosing in Special Populations: Obesity & Geriatrics (sample chapter)
PDFAmerican College of Clinical Pharmacy (ACCP)
Includes Devine IBW and adjusted body weight with a commonly used correction factor (often 0.4).
Drug dosing in obese adults (Barras, 2017)
PDFAustralian Prescriber / NPS MedicineWise
Australian overview discussing weight descriptors (TBW/IBW/ABW) and dosing considerations in obesity.
These links are provided for education. Always follow local policy and medication-specific guidance when selecting a dosing weight (TBW vs IBW vs ABW).