Adjusted Body Weight Calculator — IBW + Adjusted Weight (Devine)

Sex

Male Female

The Devine formula uses a different base weight for men and women.

Height

ft in

Example: 5 ft 10 in.

Actual body weight Your current scale weight, in pounds.

Try it: a man, 5 ft 10 in, 220 lb → ideal 73.0 kg, adjusted 83.7 kg.

Quick Answer

Adjusted body weight = ideal body weight (IBW) + 0.4 × (actual weight − IBW). Ideal body weight comes from the Devine formula: men, 50 kg + 2.3 kg for each inch over 5 feet; women, 45.5 kg + 2.3 kg for each inch over 5 feet. Example: a man who is 5 ft 10 in and weighs 220 lb (99.8 kg) has an ideal weight of 73.0 kg and an adjusted weight of 83.7 kg. Adjusted weight is mainly used when actual weight is well above ideal weight — for certain medicine doses and nutrition estimates — and it is not a personal weight-loss target.

How to use this calculator

Choose Imperial (feet and pounds) or Metric (centimeters and kilograms), select Male or Female, enter your height and your current scale weight, and press Calculate. You will get five things: your ideal body weight, your actual body weight, your adjusted body weight, your actual weight as a percentage of your ideal weight, and your BMI for context. The working is shown underneath with your own numbers, plus a plain-English line saying which weight would normally apply in your case.

The formulas, explained

Step 1: Ideal body weight (Devine)

The Devine formula, published in 1974 for dosing the antibiotic gentamicin, estimates a reference weight from height and sex alone:

Men: IBW (kg) = 50 + 2.3 × (height in inches − 60)
Women: IBW (kg) = 45.5 + 2.3 × (height in inches − 60)

The “60” is 5 feet in inches, so only the inches above 5 feet count. A man who is 5 ft 10 in is 10 inches over 5 feet, so his ideal weight is 50 + (2.3 × 10) = 73 kg. A woman of the same height is 45.5 + (2.3 × 10) = 68.5 kg. At exactly 5 feet, the formula gives the base value itself: 50 kg for men, 45.5 kg for women.

Step 2: Adjusted body weight

Adjusted body weight (kg) = IBW + 0.4 × (actual weight − IBW)

The idea is simple. Fat tissue takes up many medicines less readily than lean tissue, and it burns fewer calories per kilogram than lean tissue. So dosing or feeding someone purely on their full scale weight can overshoot, while using ideal weight alone can undershoot. Adjusted weight splits the difference: it starts at ideal weight and adds back 40% of the excess above ideal.

Note the 0.4 factor. Some protocols use a different factor — for example, some immunoglobulin dosing uses 0.5 — so 0.4 is the standard adjusted-weight convention, not a universal constant. The specific drug and the local protocol decide.

A warning about the other formula you may meet

Some calculators online use Robinson’s formula instead of Devine (men: 52 kg + 1.9 kg per inch over 5 feet; women: 49 kg + 1.7 kg per inch over 5 feet). For the same person, Robinson gives a different ideal weight, and therefore a different adjusted weight. This calculator uses Devine, because Devine is the formula most commonly tied to adjusted-weight dosing. If another site gave you a different number, check which formula it used before assuming either one is wrong.

Worked example

A man is 5 ft 10 in tall and weighs 220 lb.

Convert to metric: 5 ft 10 in = 70 inches = 177.8 cm; 220 lb = 99.8 kg.
Ideal weight: 50 + 2.3 × (70 − 60) = 50 + 23 = 73.0 kg (160.9 lb).
Excess over ideal: 99.8 − 73.0 = 26.8 kg.
Forty percent of the excess: 0.4 × 26.8 = 10.7 kg.
Adjusted weight: 73.0 + 10.7 = 83.7 kg (184.6 lb).

His actual weight is 136.7% of his ideal weight — well above it — so adjusted weight is the figure clinicians would most commonly consider for the uses below. His BMI, from actual weight, is 99.8 ÷ (1.778 × 1.778) = 31.6, in the obesity range, which is consistent with the picture but measures something different: BMI describes weight relative to height, while adjusted weight is a dosing and nutrition estimating tool.

A second check, against a widely quoted example: a man 180 cm tall weighing 100 kg has an ideal weight of 75.0 kg and an adjusted weight of 85.0 kg. If your numbers do not land near those for those inputs, check that you entered height in the right units.

When adjusted weight is used — and when it is not

Situation	Weight normally used	Why
Actual weight below ideal weight	Actual body weight	There is no excess to adjust; using a higher figure would overestimate.
Actual weight above ideal, but not by much	Often actual weight, or adjusted weight if the protocol says so	Many protocols only switch to adjusted weight at higher excess weights (commonly above 130% of ideal, or more than 20–30% above ideal, depending on the source).
Actual weight well above ideal (e.g. above 130% of ideal)	Adjusted body weight	The standard middle ground for certain medicine doses (classically aminoglycoside antibiotics such as gentamicin) and for nutrition estimates in obesity.
Ventilator settings (tidal volume)	Ideal body weight, never actual or adjusted	Lung size tracks height, not body size, so ideal weight is the reference.
Some specific drugs (e.g. some immunoglobulin dosing)	A different adjusted figure (0.5 factor) or actual weight	Dosing weight is drug-specific; never assume the 0.4 formula applies to every medicine.
Personal fitness or weight-loss goal	Neither — use a healthy BMI range and body composition instead	Ideal weight was built for dosing, not as a target for how you should look or what you should weigh.

The short version: adjusted weight matters most in clinical settings where actual weight would mislead. For everyday health and fitness, your BMI range and your body-fat level (see the Body Fat Calculator) are more useful guides.

What if my height is under 5 feet?

The Devine formula is defined for heights of 5 feet and taller. Below 5 feet, this calculator holds ideal weight at the 5-foot base value (50 kg for men, 45.5 kg for women) and flags the result as a rough estimate only. Do not use a below-5-feet result for any clinical purpose — the formula was never validated there, and for children and teenagers, weight is judged with age-based growth charts, not with this formula at all.

Common mistakes

1. Using adjusted weight as a goal weight. Adjusted weight is not a target to diet toward. It is a number clinicians use to estimate doses and energy needs. A healthy goal is better set from a BMI range, body composition, and what you can sustain.

2. Mixing up the formulas. Devine and Robinson give different ideal weights. If you compare calculators, compare the formula first — a 3–5 kg gap between sites usually means different formulas, not an arithmetic error.

3. Applying the 0.4 factor to every drug. Dosing weight is drug-specific. Some medicines dose on actual weight, some on ideal weight, some on adjusted weight with a different factor, and some on lean body weight. The calculator cannot know which applies to a given medicine.

4. Entering height in the wrong units. 5 ft 10 in is 70 inches, not 5.10 and not 58. In metric, it is 178 cm, not 1.78 entered as centimeters. The calculator’s unit toggle exists to prevent exactly this error — check which system is selected before you type.

5. Forgetting that this is an estimate. Ideal weight ignores age, muscle mass, frame size, and body composition. Two people of the same height and sex can have the same ideal weight and very different healthy weights. Treat every figure here as a starting estimate, not a verdict.

Frequently asked questions

1. What is adjusted body weight?
Adjusted body weight is ideal body weight plus 40% of the difference between actual weight and ideal weight: AdjBW = IBW + 0.4 × (actual weight − IBW). It is a middle-ground figure used when actual weight is well above ideal weight, so that doses and nutrition estimates are neither as high as full-weight figures nor as low as ideal-weight figures.

2. How do I calculate adjusted body weight?
First find ideal body weight with the Devine formula (men: 50 kg + 2.3 kg per inch over 5 feet; women: 45.5 kg + 2.3 kg per inch over 5 feet). Then subtract ideal from actual weight, multiply that excess by 0.4, and add the result to ideal weight. Example: IBW 73 kg, actual 99.8 kg → 73 + 0.4 × 26.8 = 83.7 kg.

3. What is the ideal body weight for a 5 ft 10 in man?
73 kg (161 lb) by the Devine formula: 50 + 2.3 × 10 inches over 5 feet. A woman of the same height is 68.5 kg (151 lb).

4. When do I use adjusted body weight instead of actual body weight?
Most commonly when actual weight is well above ideal weight — often described as above 130% of ideal weight, or more than 20–30% above it — for certain medicine doses and nutrition estimates. When actual weight is below ideal weight, use actual weight. The exact threshold and the choice of weight are set by the drug’s protocol, not by this calculator.

5. Is adjusted body weight the same as ideal body weight?
No. Ideal weight depends only on height and sex. Adjusted weight also uses your actual weight: it starts at ideal weight and moves 40% of the way toward your actual weight. If your actual weight equals your ideal weight, the two are the same number.

6. Can I use this calculator to work out a medicine dose?
No — not on your own. This calculator shows you the weight figure; it does not tell you which weight a given medicine requires, what dose follows from it, or whether that dose is safe for you. Medicine dosing decisions need a clinician or pharmacist, who will check the drug, the protocol, kidney function, and your full history.

Disclaimer

This calculator is for general education only and is not medical advice. Adjusted body weight and ideal body weight are clinical estimating tools with known limits: they ignore age, muscle mass, frame size, and body composition, and they are not validated below 5 feet of height or for children. Never use these results to set, change, or skip a medicine dose, a nutrition plan, or a treatment decision. For any dosing or health decision, speak to a clinician or pharmacist.

Sources

Devine BJ. Gentamicin therapy. Drug Intelligence and Clinical Pharmacy, 1974 (the original Devine ideal-weight formula).
Bauer LA, Edwards WAD, Dellinger EP, Simonowitz DA. Influence of weight on aminoglycoside pharmacokinetics in normal weight and morbidly obese patients. European Journal of Clinical Pharmacology, 1983 (adjusted-weight pharmacokinetics in obesity).
Standard adult BMI bands (underweight below 18.5, healthy range 18.5–24.9, overweight 25–29.9, obesity range 30 and above), as used for the BMI-for-context figure in the calculator.