⚖️ Adjusted Body Weight Calculator (ABW, IBW and Devine Formula)
By ToolNimba Health Team · Reviewed by ToolNimba Editorial Review, clinical content review · Updated 2026-06-21
This calculator is for general education only and is not medical advice. Adjusted body weight is a dosing and nutrition convention, not a health target, and its clinical use varies by drug, guideline and institution. The figures here do not tell you a weight you should aim for. Always follow your own clinician, pharmacist or local protocol, and never change a medication dose based on this tool.
Adjusted body weight is used when actual weight is above ideal body weight.
Adjusted body weight (ABW) is a number clinicians use when a person weighs more than their ideal body weight, mainly to help size certain medication doses and nutrition estimates. It starts from ideal body weight (IBW) calculated with the Devine formula, then adds back a fraction of the extra weight. Enter sex, height and actual weight, and this calculator returns both the ideal body weight and the adjusted body weight using the standard 0.4 correction factor.
What is the Adjusted Body Weight Calculator?
Many drug doses and energy estimates were originally studied against ideal body weight, the weight expected for a given height. In people carrying extra weight, dosing on full actual weight can overshoot, because fat tissue does not take up every drug the same way lean tissue does. Dosing on ideal weight alone, however, can undershoot, since heavier people do have more total tissue, more blood volume and larger organs. Adjusted body weight is a practical middle figure: it takes ideal body weight and adds back a portion of the difference between actual and ideal weight, so the dosing number tracks the part of excess weight that still behaves like active tissue.
The usual formula is Adjusted BW = IBW + 0.4 x (actual weight - IBW). The 0.4 is a correction factor that reflects roughly how much of excess weight behaves, for dosing purposes, like the lean tissue the original studies assumed. The remaining 0.6 of the excess is treated as relatively inert adipose tissue that does not need to be dosed for. Some references use other factors such as 0.25 or 0.5 for specific drugs or situations, so the 0.4 used here is the common default rather than a universal rule. The ideal body weight underneath it comes from the Devine formula: 50 kg for men or 45.5 kg for women at 5 feet (60 inches), plus 2.3 kg for every inch above that.
A key point is when adjusted body weight even applies. Most protocols only reach for it once actual weight passes a threshold, commonly around 120 to 130 percent of ideal body weight, which is another way of saying the person is roughly 20 to 30 percent above ideal. Below that point the gap between actual and ideal is small enough that the choice of weight rarely changes the dose, so actual or ideal weight is used directly. Adjusted body weight always sits between ideal and actual weight for a heavier person, which is exactly why it is useful as a compromise number.
One of the most common real-world uses is renal dosing. The Cockcroft-Gault equation estimates creatinine clearance, and in patients well above their ideal weight many references plug adjusted body weight (with the 0.4 factor) into that equation rather than actual or ideal weight, because it gives the most realistic clearance estimate in obesity. Some medications, though, are explicitly studied against actual body weight regardless of size, and a few against ideal weight only. There is no single weight that is correct for every drug, so the prescribing information and local protocol always win.
It also helps to keep adjusted body weight separate from the related idea of lean body weight (LBW). Lean body weight estimates only metabolically active tissue and is sometimes preferred for drugs that distribute mainly into lean mass, such as some anaesthetic agents. Adjusted body weight, by contrast, deliberately keeps a slice of the fat mass in the number. The two are not interchangeable, and picking between actual, ideal, adjusted and lean weight is a clinical decision tied to the specific medication or calculation in front of the prescriber.
Finally, remember what this number is not. Adjusted body weight is a dosing and estimation convention, not a goal weight, not a measure of health, and not a target to lose toward. It exists to scale calculations more safely in people above their ideal weight. For questions about a healthy weight, body composition or weight loss, body mass index, waist measurement and a clinician's assessment are the right tools, not the adjusted body weight figure.
When to use it
- Estimating the adjusted body weight a clinician might use when sizing certain weight-based medication doses such as aminoglycosides.
- Feeding an adjusted weight into the Cockcroft-Gault equation to estimate creatinine clearance in patients well above ideal weight.
- Helping students and trainees in pharmacy, nursing and dietetics practise the IBW and ABW calculations before exams.
- Checking how ideal body weight, actual weight and adjusted body weight relate for a given height and sex.
- Providing a quick adjusted weight figure for some clinical nutrition and energy-requirement estimates.
- Comparing adjusted body weight against actual and ideal weight to understand which dosing weight a protocol may call for.
How to use the Adjusted Body Weight Calculator
- Choose metric or imperial units.
- Select sex, since the Devine ideal weight base differs for men and women.
- Enter the height (centimetres, or feet and inches).
- Enter the actual body weight.
- Read off the ideal body weight and the adjusted body weight, updated instantly.
- Compare the three numbers (ideal, actual, adjusted) and apply only the weight your guideline specifies.
Formula & method
Worked examples
A man who is 70 inches tall (5 ft 10 in) weighs 100 kg.
- Inches over 60 = 70 - 60 = 10
- IBW = 50 + 2.3 x 10 = 50 + 23 = 73 kg
- Actual (100 kg) is greater than IBW (73 kg), so adjust
- Adjusted BW = 73 + 0.4 x (100 - 73)
- Adjusted BW = 73 + 0.4 x 27 = 73 + 10.8 = 83.8 kg
Result: IBW 73.0 kg, adjusted body weight 83.8 kg
A woman who is 65 inches tall (5 ft 5 in) weighs 90 kg.
- Inches over 60 = 65 - 60 = 5
- IBW = 45.5 + 2.3 x 5 = 45.5 + 11.5 = 57 kg
- Actual (90 kg) is greater than IBW (57 kg), so adjust
- Adjusted BW = 57 + 0.4 x (90 - 57)
- Adjusted BW = 57 + 0.4 x 33 = 57 + 13.2 = 70.2 kg
Result: IBW 57.0 kg, adjusted body weight 70.2 kg
Checking the threshold: a man 70 inches tall (IBW 73 kg) weighs 82 kg, only about 112 percent of ideal.
- IBW = 50 + 2.3 x 10 = 73 kg
- Actual / IBW = 82 / 73 = about 1.12 (roughly 112 percent of ideal)
- This is below the common 120 to 130 percent trigger for using adjusted weight
- If the formula is still applied: Adjusted BW = 73 + 0.4 x (82 - 73) = 73 + 3.6 = 76.6 kg
- Many protocols would simply dose on actual weight here, since the gap is small
Result: IBW 73.0 kg, ABW would be 76.6 kg, but at 112 percent of ideal most protocols use actual weight directly
Devine ideal body weight base and per-inch increment
| Sex | Base at 5 ft (60 in) | Per inch over 60 in |
|---|---|---|
| Male | 50 kg | +2.3 kg |
| Female | 45.5 kg | +2.3 kg |
Devine ideal body weight by height (approximate)
| Height | Male IBW | Female IBW |
|---|---|---|
| 5 ft 0 in (152 cm) | 50.0 kg | 45.5 kg |
| 5 ft 4 in (163 cm) | 59.2 kg | 54.7 kg |
| 5 ft 8 in (173 cm) | 68.4 kg | 63.9 kg |
| 5 ft 10 in (178 cm) | 73.0 kg | 68.5 kg |
| 6 ft 0 in (183 cm) | 77.6 kg | 73.1 kg |
| 6 ft 2 in (188 cm) | 82.2 kg | 77.7 kg |
How adjusted body weight grows with excess over ideal (IBW = 70 kg example)
| Actual weight | Excess over IBW | Adjusted body weight |
|---|---|---|
| 70 kg | 0 kg | 70.0 kg (no adjustment) |
| 85 kg | 15 kg | 76.0 kg |
| 100 kg | 30 kg | 82.0 kg |
| 120 kg | 50 kg | 90.0 kg |
Which weight clinicians may use (general patterns, always check the drug)
| Weight type | Typical use |
|---|---|
| Actual body weight | Many drugs, especially those dosed by total body size; some renal calculations |
| Ideal body weight | Some drugs that distribute mainly into lean tissue, and as the ABW base |
| Adjusted body weight | Patients above about 120 to 130 percent of ideal, e.g. aminoglycosides, some renal dosing |
| Lean body weight | Selected drugs that distribute into lean mass, such as some anaesthetics |
Common mistakes to avoid
- Treating adjusted body weight as a goal weight. Adjusted body weight is a dosing and estimation figure, not a target you should aim to reach. It exists to scale certain drug doses and nutrition calculations, and says nothing about a healthy weight for you.
- Using the 0.4 factor for every drug. The 0.4 correction factor is the common default, but some references and protocols use 0.25, 0.5 or no adjustment at all for specific medications. The right choice depends on the drug, so follow the relevant guideline.
- Applying adjusted weight when actual is below ideal. Adjusted body weight only applies when actual weight exceeds ideal body weight, and usually only once actual passes roughly 120 to 130 percent of ideal. If someone is at or below ideal, there is no excess to add and actual weight is used directly.
- Confusing ideal, actual, adjusted and lean weight. These are four different numbers. Ideal body weight comes from height and sex, actual weight is measured, adjusted weight sits between them, and lean body weight estimates only metabolically active tissue. They are not interchangeable.
- Plugging the wrong weight into Cockcroft-Gault. For creatinine clearance in obesity, many references use adjusted body weight, but some drugs are validated against actual or ideal weight. Using the wrong one can over or underestimate clearance, so match the weight to the medication.
- Mixing up units. The Devine constants (50 kg, 45.5 kg, 2.3 kg per inch) are metric, but height is entered in inches. Mixing pounds and kilograms or feet and centimetres without converting first gives a meaningless result.
Glossary
- Ideal body weight (IBW)
- The reference weight expected for a given height and sex, here from the Devine formula.
- Adjusted body weight (ABW)
- Ideal body weight plus a fraction (here 0.4) of the difference between actual and ideal weight, used in some dosing and nutrition calculations.
- Actual body weight (TBW)
- A person's real measured weight, sometimes called total body weight, as opposed to an ideal or adjusted estimate.
- Lean body weight (LBW)
- An estimate of body weight excluding most fat mass, counting mainly metabolically active lean tissue.
- Devine formula
- A 1974 method for estimating ideal body weight: 50 kg (men) or 45.5 kg (women) at 5 ft, plus 2.3 kg per inch above 5 ft.
- Correction factor
- The multiplier (commonly 0.4) applied to the excess weight above ideal when computing adjusted body weight.
- Cockcroft-Gault equation
- A formula for estimating creatinine clearance that takes a body weight as one of its inputs; adjusted weight is often used in obesity.
- Aminoglycosides
- A class of antibiotics (such as gentamicin) whose obesity dosing is commonly based on adjusted body weight.
Frequently asked questions
What is adjusted body weight used for?
Adjusted body weight is mainly used in healthcare to help size certain weight-based medication doses, to feed into creatinine clearance estimates, and for some clinical nutrition calculations in people who weigh more than their ideal body weight. It is a dosing convention, not a personal weight target, and which weight a clinician uses depends on the specific drug or calculation.
What is the adjusted body weight formula?
The standard formula is Adjusted BW = IBW + 0.4 x (actual weight - IBW). It takes ideal body weight and adds back 40 percent of the difference between actual and ideal weight. It is applied only when actual weight is greater than ideal body weight, and usually only once actual is well above ideal.
How is ideal body weight calculated here?
This tool uses the Devine formula: men start at 50 kg and women at 45.5 kg for a height of 5 feet (60 inches), then add 2.3 kg for every inch above that. So a 5 ft 10 in man has an ideal body weight of 50 + 2.3 x 10 = 73 kg.
Why is the correction factor 0.4?
The 0.4 factor reflects roughly how much excess weight behaves, for dosing purposes, like the lean tissue the original studies assumed, while the other 0.6 is treated as relatively inert fat. It is the common default, but some drugs and protocols use 0.25, 0.5 or none, so always follow the relevant clinical guideline.
When should I use adjusted body weight instead of actual weight?
Adjusted body weight is typically reserved for patients whose actual weight is about 120 to 130 percent of ideal body weight or more, meaning roughly 20 to 30 percent above ideal. Below that the gap is small and actual or ideal weight is usually used directly. The right weight for any given dose is decided by the drug and protocol involved.
What is the difference between adjusted body weight and lean body weight?
Adjusted body weight keeps a portion (here 40 percent) of the excess fat mass in the number, while lean body weight estimates only metabolically active tissue and excludes most fat. They are different calculations used for different drugs, so they are not interchangeable.
Which weight do I use for creatinine clearance with Cockcroft-Gault?
In patients well above ideal weight, many references use adjusted body weight (with the 0.4 factor) in the Cockcroft-Gault equation because it gives a realistic clearance estimate in obesity. However, some medications are validated against actual or ideal weight, so always check the drug-specific guidance before choosing.
Does adjusted body weight work in pounds or kilograms?
The formula works in either unit as long as you stay consistent, but the Devine ideal body weight constants are metric (50 kg, 45.5 kg, 2.3 kg per inch). This calculator handles the conversions for you when you choose imperial units, so you can enter pounds and feet and inches directly.
Is adjusted body weight a healthy weight to aim for?
No. Adjusted body weight is a calculation convention for dosing and estimation, not a recommended or healthy goal weight. For questions about a healthy weight or weight loss, speak with a qualified clinician rather than relying on this figure.
Can I use this calculator for children?
No. The Devine ideal body weight formula and the adjusted body weight convention were developed for adults. Paediatric dosing uses different weight-based and body-surface-area methods, so this tool should not be applied to children.
Sources
- Devine BJ. Gentamicin therapy (origin of the ideal body weight formula) , Drug Intelligence and Clinical Pharmacy (1974)
- Pai MP, Paloucek FP. The origin of the ideal body weight equations , Annals of Pharmacotherapy (2000)
- Ideal, Adjusted, and Nutritional Body Weight Calculator , ClinCalc (2024)