Reference Weight Formulas
Compare the Devine, Robinson, Miller, and Hamwi height-based weight formulas side by side.
What this tool does
This calculator runs a single height through four published height-based weight equations — Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) — and reports the range they span. Each formula pairs a sex-specific base weight with a fixed increment per inch of height above 5 feet. The equations originated in clinical drug-dosing practice and actuarial tables, not body-composition research, and they disagree with each other by several kilograms at most heights. The tool presents all four results side by side so the disagreement itself is visible; no single figure is a target or a measurement of any individual.
Formula Used
Disclaimer
This calculator is for educational and informational purposes only. It does not provide medical, nutritional, or training advice. Results are mathematical estimates and may not reflect individual circumstances. Consult a qualified coach, registered dietitian, medical professional, or physiotherapist for personal guidance.
How Reference Weight Formulas works
This calculator takes one height, converts it from centimetres to inches, and runs it through four published weight equations: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). Every equation has the same structure — a sex-specific base weight in kilograms plus a fixed increment for each inch of height above 5 feet (152.4 cm). The tool computes all four values, displays each in kilograms and pounds, and reports the full range they span as the headline result. The range is the point: four careful authors, working from four different datasets for four different purposes, arrived at four different answers.
The four equations
For men, the Devine formula returns 50 kg plus 2.3 kg per inch over 5 ft; Robinson returns 52 kg plus 1.9 kg; Miller returns 56.2 kg plus 1.41 kg; Hamwi returns 48 kg plus 2.7 kg. For women, Devine returns 45.5 kg plus 2.3 kg per inch; Robinson returns 49 kg plus 1.7 kg; Miller returns 53.1 kg plus 1.36 kg; Hamwi returns 45.5 kg plus 2.2 kg.
A worked example: a 175 cm man is 68.9 inches tall, 8.9 inches over 5 feet. Devine returns 50 + 2.3 × 8.9 ≈ 70.5 kg. Robinson returns 52 + 1.9 × 8.9 ≈ 68.9 kg. Miller returns 56.2 + 1.41 × 8.9 ≈ 68.7 kg. Hamwi returns 48 + 2.7 × 8.9 ≈ 72.0 kg. The spread between the lowest and highest figure is 3.3 kg — about 5% of body weight — from nothing but the choice of equation.
A second scenario: a 162.5 cm woman is 4.0 inches over 5 feet. Devine returns 54.6 kg, Robinson 55.8 kg, Miller 58.5 kg, and Hamwi 54.2 kg — a 4.3 kg spread. Note that the ordering flips: Hamwi, the highest formula for the tall man, is the lowest for the shorter woman, because Hamwi combines a low base with a steep slope while Miller pairs a high base with a shallow one. Which equation sits at the top of the range depends on height and sex.
Why the formulas disagree by design
None of these equations was derived from body-composition measurements. Hamwi's constants appeared in a 1964 clinical text on diabetes management as a bedside estimation shortcut. Devine's 1974 figures were published for calculating drug doses — gentamicin dosing scales with lean tissue rather than total weight, and Devine needed a height-based stand-in. Robinson and Miller both re-fitted Devine's structure in 1983 against Metropolitan Life insurance tables and reached different constants from the same exercise. Four datasets, four eras, four purposes: the disagreement is structural, not an error one more decimal place could fix. Treating any single output as a personal target misreads what the numbers are — the spread across formulas is the finding this tool reports.
Where the arithmetic drifts
Below 5 feet, every equation extrapolates: the linear term goes negative, producing figures the original authors never modelled or validated. Devine himself noted the formula's limits at short stature. At tall heights the fixed per-inch slope compounds — at 200 cm the four formulas span roughly 5 kg, and none accounts for frame breadth, muscle mass, age, or bone density. Two people of identical height can differ by 15 kg of lean tissue alone; a height-only equation cannot see that. The formulas also assume the sex-specific averages of mid-20th-century North American reference populations, which shift across time and ancestry.
What this tool does not do
The calculator performs four multiplications and reports the results. It does not assess body composition, set a goal weight, evaluate health status, or rank the formulas against each other. A figure outside the displayed range carries no judgement of any kind — athletes, in particular, routinely weigh more than all four outputs while carrying low body fat. Tools that measure something (waist-to-height ratio, body-fat estimation) sit alongside this one for readers who want quantities with a physical interpretation.
Disclaimer
This tool is for educational and informational purposes only. It is not medical, nutritional, or training advice. The outputs are published mathematical estimates from historical clinical literature and do not describe any individual's body. Consult a qualified healthcare provider or registered dietitian for personal assessment.
Questions
- Why do the four formulas give different numbers for the same height?
- Because they were fitted by different authors, in different decades, against different data, for different purposes. Hamwi (1964) published a bedside shortcut for clinical estimation; Devine (1974) needed a lean-tissue stand-in for drug dosing; Robinson and Miller (both 1983) re-fitted the same linear structure against insurance actuarial tables and still landed on different constants. A 3–4 kg disagreement at ordinary heights is not a rounding problem — it reflects genuinely different source populations and goals. That disagreement is why this tool shows all four rather than averaging them into a single number that none of the authors published.
- Why do many calculators give these formulas a different name?
- The clinical literature's historical label for this family of equations is "ideal body weight (IBW)" — a naming convention that dates to mid-20th-century pharmacology and actuarial work, examined in detail by Pai and Paloucek (2000). The name described a dosing reference quantity, not a judgement about anyone's body, but it reads today like a prescription. This site uses "reference weight" throughout because that is what the numbers are: published reference points from four historical equations, useful for understanding drug-dosing conventions and the history of anthropometry, not targets.
- Were these formulas derived from health outcome data?
- No. None of the four equations came from studies linking weight to health outcomes, and none involved body-composition measurement. Devine's constants were proposed for scaling gentamicin and other drug doses; Hamwi's appeared in a diabetes-management text as an estimation aid; Robinson's and Miller's were regression fits to Metropolitan Life insurance tables, which recorded policyholder mortality in mid-century North America. The formulas encode the height–weight relationships of those specific datasets and nothing more, which is one reason they diverge from each other and from modern population measurements.
- What happens for heights below 5 feet?
- The equations were published as a base weight at 5 feet plus an increment per inch above it. Below 152.4 cm the per-inch term turns negative and the arithmetic extrapolates into territory the original authors never modelled — Devine's formula, for example, sheds 2.3 kg per inch and produces figures with no published validation at short statures. This calculator still computes the extrapolated values so the behaviour of the equations is visible, but below 5 feet the outputs are best read as a demonstration of the formulas' limits rather than as reference points.
- Which formula appears most often in clinical practice?
- Devine's 1974 equation is the most widely cited, largely because pharmacokinetic dosing references adopted it for medications that scale with lean tissue — aminoglycosides are the classic case — and hospital dosing software carried it forward. Robinson and Miller appear in the literature as refinements with better fit to actuarial data, and Hamwi survives mainly in older clinical texts. Prevalence in dosing references reflects institutional momentum rather than a demonstrated accuracy ranking; comparative studies find each formula fits some height bands better than others.
Sources & Methodology
Height in cm is divided by 2.54 to give inches; each formula adds a sex-specific base to a slope times (inches − 60). Men: Devine = 50 + 2.3/in, Robinson = 52 + 1.9/in, Miller = 56.2 + 1.41/in, Hamwi = 48 + 2.7/in. Women: Devine = 45.5 + 2.3/in, Robinson = 49 + 1.7/in, Miller = 53.1 + 1.36/in, Hamwi = 45.5 + 2.2/in. All outputs in kg; pounds computed at 2.2046 lb/kg. The headline result is the minimum-to-maximum range across the four formulas. Below 152.4 cm the linear term extrapolates outside the published derivation range.
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