Ideal Body Weight Calculator

By Rick Campbell · Updated 12 Sept 2026 · Sourced to primary literature · Not medical advice

Ideal body weight is not a health target. It is a clinical estimate of what a person of a given height and sex would weigh without excess fat, invented so that drugs could be dosed against something steadier than the number on the scale. Four equations dominate: Hamwi (1964), Devine (1974), Robinson (1983) and Miller (1983). This page runs all four, names each one, and shows the weight it returns next to the BMI that weight works out at for your height.

That second column is the point. On its own, an ideal weight of 75 kg means nothing; read as BMI 23.1 at 180 cm, it is obviously one point inside a healthy band rather than a line you have failed to reach. The four formulas usually land between BMI 21 and 24, so they are not in dispute about health; they are in dispute about which mid-century insurance table to trust, and at the extremes of height that disagreement reaches ten kilograms and more.

If you want to know where your own weight sits, and how much room you have either side of it, the page you actually want is the healthy weight range calculator. It takes a current weight and tells you exactly how far you are from each edge of the band. This page is for the formulas themselves: their constants, their provenance, the drug and ventilator calculations that still use them every day, and the honest limits of asking a 1974 dosing rule to set a personal goal.

In brief

Ideal body weight equations were built for drug dosing, not health: Hamwi (1964) for insulin at the bedside, Devine (1974) for gentamicin, Robinson and Miller (both 1983) as regression refits of the same height-weight tables.
All four share one shape (a base weight at five feet plus a fixed increment per inch above it) and differ only in those two constants, which is why they agree at 152 cm and diverge by ten kilograms or more above 190 cm.
Devine is the most quoted because pharmacy adopted it; in metric form it is the ARDSNet predicted body weight used to set ventilator tidal volumes at 6 ml per kilogram.
For a hydrophilic drug in a person with obesity, clinicians use adjusted body weight (ideal weight plus 40 per cent of the excess over it) rather than either extreme.
For a personal target, the WHO healthy weight range for your height is the better answer, because the evidence supports a band roughly twenty kilograms wide, not a point.

What you'll see here

All four classic ideal body weight formulas for your height (Hamwi, Devine, Robinson and Miller), each with the BMI that weight implies, the spread between them on a measurement rule, the WHO healthy weight range as the counterpoint, and, if you add a wrist measurement, your frame size with the conventional ±10% adjustment applied.

The published constants, per sex

Base weight at 5 ft and the increment added for each inch above it (kilograms, as published)
Formula	Men: base at 5 ft	Men: per inch over	Women: base at 5 ft	Women: per inch over
Hamwi (1964)	48 kg	2.7 kg	45.5 kg	2.2 kg
Devine (1974)	50 kg	2.3 kg	45.5 kg	2.3 kg
Robinson (1983)	52 kg	1.9 kg	49 kg	1.7 kg
Miller (1983)	56.2 kg	1.41 kg	53.1 kg	1.36 kg

Every one of these equations is anchored at five feet and is linear in inches above it, which is why they are unreliable at the extremes of height: below 152 cm there is nothing left to subtract, and above about 190 cm the differences in slope (2.7 kg an inch for Hamwi against 1.41 kg for Miller in men) compound into a disagreement of ten kilograms or more.

Where the four formulas came from

Every one of these equations traces back to the same source material: the Metropolitan Life Insurance Company height-weight tables, which were built to price policies by correlating body weight with mortality claims, not to define health. Pai and Paloucek reconstructed the lineage in 2000 and concluded that the formulas resemble each other precisely because they were all fitted to broadly agreeing versions of those tables.

George Hamwi published his rule in 1964 in an American Diabetes Association treatment volume, a bedside shortcut for estimating the calorie and insulin needs of a person with diabetes, designed to be done in the head: 48.0 kg for a man of five feet, 45.5 kg for a woman, plus 2.7 kg or 2.2 kg for every inch above that. Benjamin Devine published his in 1974 inside a clinical pharmacy case study on gentamicin therapy, an aminoglycoside antibiotic that distributes into lean tissue rather than fat and will damage kidneys and hearing if the dose is scaled to total body weight in a person with obesity.

Robinson and colleagues, and Miller and colleagues, both published in the American Journal of Hospital Pharmacy in 1983, each refitting the same idea against newer tabulated data. Robinson's constants are lower than Devine's for men and higher for women; Miller's are much higher at the base and much flatter per inch, which is why Miller returns the highest figure for short people and the lowest for tall ones. None of the four was ever tested as a predictor of health outcomes, and none claims to be.

Why the four formulas disagree, and by how much

The disagreement is structural. Each equation is linear in inches above five feet, so the differences in slope compound with height: 2.7 kg per inch for Hamwi in men against 1.41 kg for Miller is a gap of 1.29 kg for every inch you stand above 152 cm. At 165 cm the four answers for a man sit inside three kilograms of each other. At 180 cm the spread is about six kilograms. At 195 cm it is over thirteen.

In the other direction the formulas simply stop. Below five feet there is no negative-inches term in the original publications, so this calculator clamps the term at zero rather than extrapolating a number no author ever sanctioned. That means every formula returns its flat base weight for anyone under 152.4 cm, which is a visible signal that the equations have run out of evidence rather than a real estimate.

Lemmens, Brodsky and Bernstein proposed a cleaner alternative in 2005 for anaesthesia in bariatric surgery: ideal body weight equals 22 multiplied by height in metres squared, that is, whatever weight puts you at exactly BMI 22, with no sex term at all. It behaves sensibly at every height, and its very existence makes the point that a single ideal weight is a modelling choice rather than a discovered fact.

At 152 cm and below, all four equations return their base constant; the term above five feet is zero.
At 180 cm the four answers for a man span roughly 71.5 kg to 77.3 kg, a spread of about 5.8 kg.
At 195 cm the same four span roughly 79.8 kg to 93.3 kg, a spread of about 13.5 kg, wider than most people's entire weight-loss goal.
Across ordinary adult heights the four sit between about BMI 21 and BMI 24, which is squarely inside the healthy band.

How clinicians still use ideal body weight today

Aminoglycoside antibiotics are the classic case. Gentamicin, tobramycin and amikacin are hydrophilic: they distribute into lean tissue and extracellular water and barely enter fat. Dose them on total body weight in a person carrying forty kilograms of adipose tissue and the peak concentration overshoots, with nephrotoxicity and irreversible hearing damage as the consequences. Dose them on ideal body weight alone and a person with obesity is under-treated, because adipose tissue still carries some extracellular water. Neither extreme is right, which is where adjusted body weight comes in.

The same logic reaches beyond antibiotics. Creatinine clearance estimated with the Cockcroft-Gault equation is conventionally calculated on ideal or adjusted weight rather than total weight, because a large fat mass does not generate creatinine. Neuromuscular blocking agents in anaesthesia, certain chemotherapy protocols, and heparin and thrombolytic dosing all have body-size rules for the same reason: the volume the drug actually occupies is closer to lean mass than to whatever the scale says.

Aminoglycoside and other hydrophilic antibiotic dosing, where total body weight would overshoot.
Cockcroft-Gault creatinine clearance, conventionally run on ideal or adjusted weight.
Ventilator tidal volume in critical care, which uses predicted body weight from height and sex.
Anaesthetic and neuromuscular blocker dosing, where lean mass drives the required dose.
Nutrition support, where energy and protein targets in obesity are often prescribed per kilogram of adjusted weight.

Predicted body weight and the ventilator

The most consequential modern use of an ideal weight equation is lung-protective ventilation. In the ARDS Network trial published in the New England Journal of Medicine in 2000, patients ventilated at 6 ml per kilogram of predicted body weight had lower mortality than those ventilated at the then-traditional 12 ml/kg, and the trial was stopped early. Predicted body weight in that protocol is 50 + 0.91 × (height in cm − 152.4) for men and 45.5 + 0.91 × (height in cm − 152.4) for women, which is the Devine equation restated in centimetres, since 2.3 kg per inch is 0.906 kg per centimetre.

The reason it must be predicted weight rather than actual weight is anatomical: lung volume scales with height, not with body fat. A 180 cm man weighing 75 kg and a 180 cm man weighing 130 kg have almost identical lungs, and setting the ventilator from the scale would deliver nearly twice the safe volume to the heavier patient. Contemporary practice targets roughly 6 to 8 ml per kilogram of predicted body weight in most ventilated patients, staying at the lower end in acute respiratory distress syndrome. At 180 cm, a man's predicted body weight is about 75 kg, so 6 ml/kg is about 450 ml per breath, the same figure this page's Devine row returns.

Adjusted body weight, and when actual weight wins

Adjusted body weight splits the difference: ideal body weight plus 40 per cent of the amount by which actual weight exceeds it. For a 180 cm man weighing 110 kg with a Devine ideal weight of 75.0 kg, that is 75.0 + 0.4 × (110 − 75.0) = 89.0 kg. The 0.4 factor is an empirical estimate of the share of excess mass that is metabolically active lean tissue and extracellular fluid rather than pure fat; it is a pragmatic correction, widely used and rarely defended as precise.

Which weight to use depends on the drug, not on the patient's preference. Lipophilic drugs that distribute into fat (many anaesthetic induction agents, some benzodiazepines) are dosed closer to total body weight. Hydrophilic drugs use ideal or adjusted weight. Body surface area, calculated from height and actual weight, governs most cytotoxic chemotherapy. Any calculator, this one included, can only show you the numbers; the choice between them is a prescribing decision that belongs to the clinician in front of the patient.

Body frame size and the plus or minus ten per cent convention

Enter a wrist measurement and this page will also show your frame size on the height-to-wrist convention and apply the traditional ten per cent adjustment to all four formula figures: down ten per cent for a small frame, unchanged for medium, up ten per cent for large. It is included because clinicians and dietitians have used it for decades and people expect to see it, and it is labelled as a convention because that is all it is.

The honest position: the height-to-wrist ratio is a rule of thumb from clinical anthropometry with no outcome validation behind its boundaries, and no trial has shown that a frame-adjusted ideal weight predicts drug handling or health better than the plain figure. Elbow breadth read against the Metropolitan Life frame tables, as tabulated by Frisancho in 1984, has better documentation, and our body frame size calculator offers both methods with their limits spelled out. Wrist circumference does at least correlate with skeletal size, so as a tie-breaker between two numbers three kilograms apart it is defensible; as a reason to move a target by eight kilograms it is not.

What ideal body weight is not

It is not a goal weight. No study has ever shown that people who reach their Devine or Hamwi weight live longer or suffer less illness than people who sit elsewhere in the healthy band. The equations were reverse-engineered from actuarial tables built on self-reported heights and shoe-wearing measurements taken from insured, largely white, mid-twentieth-century Americans, and they carry every bias that implies.

It is also blind to body composition, in exactly the way BMI is. A formula that sees only height and sex cannot know whether the twelve kilograms between you and its answer are fat or muscle. A rugby forward and a sedentary office worker of the same height get the same ideal weight, and the equation has no way to be right about both. If you want that distinction, measure it: our body fat calculator uses tape measurements, and the waist-to-height ratio gives the fat-distribution signal that ideal weight cannot.

Finally, it is not defined for children or teenagers. Growth is not linear in inches over five feet, and a formula anchored at adult proportions has no meaning for a body still developing. BMI-for-age percentile charts are the right tool there, which is what our child BMI calculator uses.

Ideal weight or healthy range: which page do you want

If you have arrived here because a form, a pharmacist or a piece of software asked for an ideal body weight, this page is the one you want: it names the formula, shows the constants and gives you all four answers so you can see which one your source is using. If you have arrived because you want to know what you should weigh, the healthy weight range calculator is the better page: it takes your height and your current weight and tells you where you sit in the WHO band, how far you are from each edge, and what the Asia-Pacific and older-adult evidence adds to that picture.

The two answers are not in conflict. Every formula on this page lands inside the healthy range for the same height. The difference is that a formula hands you a point and a range hands you the truth: a span of about twenty kilograms within which muscle mass, frame, ancestry and waist circumference decide where you belong.

How it's calculated

Hamwi (1964)

Men: 48.0 kg + 2.7 kg x (inches over 5 ft) · Women: 45.5 kg + 2.2 kg x (inches over 5 ft)

A bedside rule for estimating diabetic diets and insulin needs, published in an American Diabetes Association treatment volume. The steepest per-inch slope of the four.

Devine (1974)

Men: 50.0 kg + 2.3 kg x (inches over 5 ft) · Women: 45.5 kg + 2.3 kg x (inches over 5 ft)

Published inside a gentamicin dosing case study; the most cited of the four and the basis of ventilator predicted body weight.

Robinson (1983)

Men: 52.0 kg + 1.9 kg x (inches over 5 ft) · Women: 49.0 kg + 1.7 kg x (inches over 5 ft)

A regression refit of the Metropolitan Life height-weight tables, published in the American Journal of Hospital Pharmacy.

Miller (1983)

Men: 56.2 kg + 1.41 kg x (inches over 5 ft) · Women: 53.1 kg + 1.36 kg x (inches over 5 ft)

The highest base and the flattest slope: highest answer for short adults, lowest for tall ones.

Predicted body weight (ARDSNet, 2000): Devine in centimetres

Men: 50 + 0.91 x (height cm − 152.4) · Women: 45.5 + 0.91 x (height cm − 152.4) · Tidal volume = 6 ml/kg of PBW

Used to set ventilator tidal volumes, because lung size scales with height rather than with body fat.

Adjusted body weight

ABW = IBW + 0.4 x (actual weight − IBW)

Used for hydrophilic drugs in people with obesity, on the estimate that about 40% of excess mass is metabolically active tissue.

Lemmens (2005), the BMI-22 alternative

IBW = 22 x (height in metres)²

A single sex-neutral equation proposed for anaesthesia; behaves sensibly at every height instead of stopping at five feet.

The BMI a formula weight implies, and the frame convention

BMI = formula weight ÷ (height in metres)² · Frame-adjusted weight = formula weight x 0.9 (small), 1.0 (medium) or 1.1 (large)

The BMI column is how you tell that four different answers are four points inside one healthy band. The frame multiplier is a convention, not a validated correction.

Worked example: a man of 180 cm, with and without a frame adjustment

Convert height to inches over five feet: 180 ÷ 2.54 = 70.87 in, minus 60 = 10.87 inches above five feet.
Hamwi: 48.0 + 2.7 × 10.87 = 48.0 + 29.34 = 77.3 kg.
Devine: 50.0 + 2.3 × 10.87 = 50.0 + 24.99 = 75.0 kg.
Robinson: 52.0 + 1.9 × 10.87 = 52.0 + 20.65 = 72.6 kg.
Miller: 56.2 + 1.41 × 10.87 = 56.2 + 15.32 = 71.5 kg. The four answers span 5.8 kg.
Read each back as BMI at 1.80 m (3.24 m²): Hamwi 23.9, Devine 23.1, Robinson 22.4, Miller 22.1. Every one of them is inside the healthy band, which runs 59.9 kg to 80.7 kg at this height.
Ventilator check: predicted body weight is 50 + 0.91 × (180 − 152.4) = 75.1 kg, so a lung-protective tidal volume at 6 ml/kg is about 450 ml, the same answer as the Devine row, as it should be.
Add a 16.5 cm wrist: 180 ÷ 16.5 = 10.9, which is above the 10.4 male boundary, so the convention calls that a small frame and knocks ten per cent off each figure: Devine becomes 67.5 kg. Treat that as a convention, not a correction.
If this man actually weighs 110 kg and needs a gentamicin dose, the relevant number is neither 110 nor 75.0 but adjusted body weight: 75.0 + 0.4 × (110 − 75.0) = 89.0 kg.

Where this number is used in the real world

Dosing aminoglycoside antibiotics such as gentamicin and tobramycin, which distribute into lean tissue and are toxic if scaled to total body weight.
Setting ventilator tidal volumes at 6 to 8 ml per kilogram of predicted body weight, the lung-protective standard since the ARDS Network trial of 2000.
Estimating creatinine clearance with Cockcroft-Gault, conventionally run on ideal or adjusted weight rather than the scale reading.
Calculating adjusted body weight for drug dosing and nutrition support in people with obesity.
Anaesthesia, where induction agents and neuromuscular blockers are dosed against different body-size measures depending on how lipophilic they are.
Filling in a clinical form, protocol or piece of software that asks for an ideal body weight without saying which equation it means.
Understanding a number a health app or insurer has quoted at you, by finding which of the four formulas produced it.

Frequently asked questions

Which ideal weight formula should I use?

For a clinical calculation, use the one your protocol specifies; that is usually Devine, because pharmacy adopted it and ventilator predicted body weight is built on it. For a personal question about what you should weigh, none of them is the right tool, because none was derived or validated as a health target. They are drug-dosing conveniences from 1964 to 1983 that happen to output kilograms, and the healthy weight range for your height is the defensible answer instead.

Why do the four formulas give different answers?

Because each was fitted to a slightly different version of the Metropolitan Life height-weight tables with a different base weight and a different increment per inch. All four share the same linear shape, so small differences in slope compound with height: 2.7 kg per inch for Hamwi against 1.41 kg for Miller means the two answers diverge by roughly 1.3 kg for every inch you stand above five feet. At 195 cm the four span more than thirteen kilograms, which is the clearest possible evidence that a single ideal weight is a modelling choice.

What is the difference between ideal body weight and predicted body weight?

Almost nothing, mathematically. Predicted body weight as used in critical care is the Devine equation rewritten in centimetres: 50 plus 0.91 kilograms for each centimetre above 152.4 for men, and 45.5 plus the same increment for women. The name changed because the context changed. Critical care needed a height-based estimate of lung size to set ventilator tidal volumes, and calling it predicted rather than ideal avoids implying that the patient ought to weigh it.

What is adjusted body weight and when is it used?

Adjusted body weight is ideal body weight plus forty per cent of the excess of actual weight over it, and it is used when a drug distributes mainly into lean tissue but the person carries a large fat mass. Dosing such a drug on total weight risks toxicity; dosing it on ideal weight alone under-treats, because adipose tissue still holds extracellular water. The 0.4 factor is an empirical estimate of the metabolically active share of excess mass rather than a precise physiological constant.

Does ideal body weight account for muscle or frame size?

No. These equations see height and sex and nothing else, so a heavily muscled athlete and a sedentary person of identical height receive identical answers. The traditional remedy is the plus or minus ten per cent frame adjustment shown on this page when you enter a wrist measurement, but that is a long-standing convention rather than a validated correction, and no trial has shown it improves either health prediction or drug dosing. Measuring body fat or waist-to-height ratio gives you the information the formulas are missing.

Do these formulas work for very short or very tall people?

Poorly at both ends. Every equation is anchored at five feet with a linear inches-above term, so below 152.4 cm there is nothing to add and this calculator returns the flat base constant rather than extrapolating a figure the original authors never published. At the tall end the formulas do not fail so much as disagree: above 190 cm they span more than ten kilograms. The Lemmens 2005 alternative, which simply sets ideal weight at BMI 22, behaves sensibly across the whole range.

Is ideal body weight the same as the healthy weight range?

No, and the difference matters. Ideal body weight is a single number produced by a formula built for drug dosing. The healthy weight range is the span of weights corresponding to BMI 18.5 to 24.9 at your height, roughly twenty kilograms wide for most adults, across which health outcomes are broadly similar. Every formula on this page lands inside that range, which tells you the formulas are not wrong so much as falsely precise. If you want a personal target, use the range.

Why does an ideal weight calculator ask for my sex?

Because three of the four equations carry different constants for men and women, reflecting the sex-specific height-weight tables they were fitted to. Devine, for instance, starts at 50.0 kg for a man of five feet and 45.5 kg for a woman, with the same 2.3 kg per inch after that. If neither category describes you well, run both and read the interval between them as the honest answer, which is the same advice we give for every sex-specific formula on this site.

Keep going

A single number rarely tells the whole story. Alongside the ideal weight result, the healthy weight range calculator, the BMI calculator, the frame size calculator, the lean body mass calculator and the BSA calculator each add a different angle on the same measurements. For the reasoning behind the numbers, read BMI explained, BMI for athletes and BMI vs body fat vs waist.

Sources

Pai MP, Paloucek FP. The origin of the 'ideal' body weight equations. Ann Pharmacother 2000;34:1066-9. doi.org/10.1345/aph.19381
Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm 1983;40:1016-9. doi.org/10.1093/ajhp/40.6.1016
Miller DR, Carlson JD, Lloyd BJ, Day BJ. Determining ideal body weight (and mass). Am J Hosp Pharm 1983;40:1622-7. doi.org/10.1093/ajhp/40.10.1622a
Lemmens HJM, Brodsky JB, Bernstein DP. Estimating ideal body weight: a new formula. Obes Surg 2005;15:1082-3. doi.org/10.1381/0960892054621350
The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342:1301-8. doi.org/10.1056/NEJM200005043421801
WHO Expert Committee. Physical status: the use and interpretation of anthropometry. WHO Technical Report Series 854, Geneva, 1995. www.who.int/publications/i/item/9241208546
Frisancho AR. New standards of weight and body composition by frame size and height for assessment of nutritional status of adults and the elderly. Am J Clin Nutr 1984;40:808-19. doi.org/10.1093/ajcn/40.4.808

Cite this page

Quoting a figure from here in an article, a report or a piece of coursework? Use whichever of these your style guide asks for.

APA: Campbell, R. (2026). Ideal Body Weight Calculator. Body Stats. https://bodystats.co/app/ideal-weight-calculator
Plain text: “Ideal Body Weight Calculator”, Body Stats, last updated 12 September 2026, https://bodystats.co/app/ideal-weight-calculator

Every formula and threshold on this page is written out with its primary source on our methodology page. These results are informational and educational, not a diagnosis or a substitute for professional advice. See the medical disclaimer.

Last updated 12 September 2026. Written by Rick Campbell; not medically reviewed. See review status.