Adjusted Body Weight Calculator
Calculate Ideal Body Weight (IBW, Devine) and Adjusted Body Weight (AdjBW) from height, sex and actual weight.
Did this tool work for you?
How to use this calculator
The Devine formula calculates IBW from height. AdjBW moves 40% of the way from IBW to actual weight; references use it for drugs that distribute partly into body fat. The tool always calculates it and separately flags whether actual weight exceeds its built-in 130% of IBW line.
- 1
Select the patient's sex.
- 2
Enter height in centimetres and actual body weight in kilograms.
- 3
Read the calculated IBW, the adjusted body weight and the percentage by which actual weight exceeds IBW.
- 4
The Yes/No row only reports whether actual weight is above the tool’s built-in 130% of IBW line; which weight a drug uses is set by its own reference.
Frequently asked questions
Which formulas does this tool use?
It uses the Devine ideal body weight equation and a 0.4 adjustment. Ideal body weight is 50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch of height over 60 inches (152.4 cm). Adjusted body weight is then ideal weight + 0.4 × (actual weight − ideal weight). Height is entered in centimetres and weight in kilograms, and the tool converts to inches internally.
When does the tool say Yes on the 130% row?
The “Above 130% of IBW?” row says Yes when actual weight is more than 130% of the ideal body weight it calculated, and No otherwise. That 130% cut-off is the rule built into this tool, not a universal standard. Drug references and hospital protocols set their own thresholds and name which weight to use for each drug.
Why is an adjusted weight still shown when the answer is No?
The highlighted adjusted weight is always calculated from the formula, even for a person close to ideal weight. A woman of 160 cm and 60 kg gets 55.4 kg with the row below reading No. The Yes/No row and the 130% line show which side of the tool’s own line the weight falls on.
What happens for very short heights?
The tool does not stop the formula at 5 feet. Below 152.4 cm the height term turns negative and ideal weight falls under the 45.5 kg or 50 kg base; a woman of 140 cm gets 34.3 kg. The Devine equation is not validated for heights under 5 feet or for children, and this tool has no paediatric mode. If the equation would give an ideal weight of 0 or less, the tool returns an error.
What if I leave height or weight blank?
Clearing a box counts as 0 on this page, and a 0 for either value returns an error naming that field instead of a result. The tool does not substitute a default. Negative numbers are treated as zero.
Does 0.4 suit every drug?
No. The 0.4 factor is a single fixed value in this tool. Some drugs are dosed on ideal weight, some on actual weight and some use a different fraction, so the drug’s own reference decides. The tool gives no doses, maximum doses or renal adjustments.
Does it account for sex beyond the base weight?
Only through the base figure, 50 kg versus 45.5 kg. It has no inputs for age, pregnancy, body composition, oedema or fluid status, all of which can make a measured weight misleading.
Can it be used to choose a dose?
No. It returns weights only. A pharmacist or prescriber chooses the dosing weight and the dose.
Adjusted body weight calculator — Devine ideal weight with a 0.4 adjustment
Two steps from height and weight
The first step estimates an ideal body weight from height and sex using the Devine equation: 50 kg (men) or 45.5 kg (women) plus 2.3 kg for each inch above 60 inches. The second step moves 40% of the way from that ideal weight toward the person’s actual weight. The result sits between the two, closer to ideal. Some pharmacology references use this middle figure for drugs that spread only partly into body fat; the 0.4 factor is a common default and others exist. Ideal weight is also used on its own in some settings, for example when sizing ventilator tidal volumes, so the tool prints it separately from the adjusted figure and shows the percentage by which actual weight exceeds it.
Five runs of the calculator
Each row below gives the inputs and the five values the calculator returned for them. The woman at 160 cm and 60 kg is the contrast case: her adjusted weight is displayed, but the 130% row says No.
| Inputs | Ideal weight | Adjusted weight | % over ideal | Above 130%? |
|---|---|---|---|---|
| Man, 175 cm, 100 kg | 70.5 kg | 82.3 kg | 41.9% | Yes |
| Man, 175 cm, 130 kg | 70.5 kg | 94.3 kg | 84.5% | Yes |
| Woman, 160 cm, 95 kg | 52.4 kg | 69.4 kg | 81.4% | Yes |
| Woman, 160 cm, 60 kg | 52.4 kg | 55.4 kg | 14.5% | No |
| Woman, 140 cm, 50 kg | 34.3 kg | 40.6 kg | 45.9% | Yes |
Reading the 175 cm man’s rows
Raising his weight from 100 kg to 130 kg moves the adjusted figure from 82.3 kg to 94.3 kg. That is a 30 kg gain in actual weight producing a 12 kg gain in adjusted weight, because only 40% of the excess is counted. Ideal weight stays at 70.5 kg since it depends on height and sex alone.
The 130% rule and its limits
This tool reports “Yes” once actual weight passes 130% of ideal, and a note line changes wording accordingly. References use a range of thresholds, and 130% is simply the cut-off written into this tool. It does not choose a drug, a dose or an interval, and it has no checks for kidney function, age or oedema. Short stature is a further limit, as the 140 cm row shows: the Devine base is stretched below 5 feet. Entering the height in inches or the weight in pounds instead of centimetres and kilograms would distort every line, so check the units shown beside each field before reading the output.
General information only
The page shows how these weights are derived and lets you check arithmetic. It is general information, not medical advice and not for clinical decisions. The prescriber or pharmacist chooses which weight a given drug uses and checks that against the drug’s reference and local protocol.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →