How Ideal Weight Calculator works
Methodology for the Ideal Weight Calculator: formulas, coefficients, data sources, assumptions, and known limitations.
Scope
Reports an 'ideal weight' range using four classic height-based formulas (Devine, Robinson, Miller, Hamwi) so that the user sees a band, not a single number.
These formulas were built for medical dosing and actuarial tables, not for athletic performance. Treat the output as reference, not a goal.
Formula
Each formula shares the shape: ideal_weight_kg = base + per_inch_over_5ft * inches_over_5ft. Constants differ per formula and by sex.
Coefficients
| Parameter | Value | Note |
|---|---|---|
| Devine (M) | 50 kg + 2.3 kg per inch over 5 ft | |
| Devine (F) | 45.5 kg + 2.3 kg per inch over 5 ft | |
| Robinson (M) | 52 kg + 1.9 kg per inch over 5 ft | |
| Robinson (F) | 49 kg + 1.7 kg per inch over 5 ft | |
| Miller (M) | 56.2 kg + 1.41 kg per inch over 5 ft | |
| Miller (F) | 53.1 kg + 1.36 kg per inch over 5 ft | |
| Hamwi (M) | 48 kg + 2.7 kg per inch over 5 ft | |
| Hamwi (F) | 45.5 kg + 2.2 kg per inch over 5 ft |
Data sources
- Pai MP, Paloucek FP. The origin of the 'ideal' body weight equations. Ann Pharmacother. 2000;34(9):1066-1069. — PMID 10981254. Primary peer-reviewed review of the Devine, Robinson, Miller, and Hamwi formulas and their origins.
- Robinson JD, Lupkiewicz SM, Palenik L, et al. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm. 1983;40(6):1016-1019. — PMID 6869387. Source of the Robinson coefficients.
- Miller DR, Carlson JD, Loyd BJ, Day BJ. A comparative evaluation of three methods for determining ideal body weight. Drug Intell Clin Pharm. 1983;17(3):198-200. — PMID 6825033. Source of the Miller coefficients.
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8(11):650-655. — Original Devine formula, built for aminoglycoside dosing — SAGE journal archive copy.
- Hamwi GJ. Therapy: changing dietary concepts. In: Danowski TS, ed. Diabetes Mellitus: Diagnosis and Treatment. New York: American Diabetes Association, 1964:73-78. — Textbook chapter; no peer-reviewed primary source for the Hamwi coefficients — see Limitations.
Assumptions
- Height is measured without shoes.
- The four formulas are weighted equally in the displayed range; no formula is judged superior.
Approximation range
The four-formula spread is typically 5–10 kg at adult heights. That spread is the useful signal, not the mean.
None of the formulas were validated on muscular populations; heavy-training athletes routinely weigh well above 'ideal'.
Limitations
- All four formulas are older than modern body-composition science. They encode height, not lean mass.
- Not suitable for people under ~150 cm or over ~200 cm; the per-inch term extrapolates poorly at the extremes.
- Use FFMI, body-fat percentage, and performance metrics for athletic goals, not ideal-weight formulas.
Reproducibility
Male, 180 cm (~70.9 in; 10.9 in over 5 ft). Devine = 50 + 2.3*10.9 = 75.1 kg. Robinson = 52 + 1.9*10.9 = 72.7 kg. Miller = 56.2 + 1.41*10.9 = 71.6 kg. Hamwi = 48 + 2.7*10.9 = 77.4 kg. Displayed range: 71.6–77.4 kg.
Change log
- 2026-04-24: methodology page first published.
Related tools
- BMI Calculator — Calculate BMI quickly with a plain-language range explanation and limitations.
- Body Fat Percentage Calculator — Estimate body fat percentage using the U.S. Navy circumference method.
- Waist-to-Hip Ratio Calculator — Calculate waist-to-hip ratio and assess body composition using WHO guidelines.
- FFMI Calculator — Calculate Fat-Free Mass Index to gauge muscularity and compare against natural benchmarks.
Worked example
Computed by the same engine bundle served at
/engines/ideal-weight-calculator.js. Re-runnable: the values below
are the literal output of compute(engineInput).
Input
- tool
- ideal_weight_calculator
- sex
- male
- height_cm
- 178
Output
- devineKg
- 73.181102
- robinsonKg
- 71.149606
- millerKg
- 70.411024
- hamwiKg
- 75.212598
- minKg
- 70.411024
- maxKg
- 75.212598
FAQ
- Which formula is used here?
- Shows Devine, Robinson, Miller, and Hamwi formula estimates as a range rather than a single rigid target.
- Can I use metric or imperial units?
- Yes. This tool supports both metric and imperial units and remembers your preference.
- Is this medical advice?
- No. This tool provides general fitness estimates and should not replace medical guidance.
- Is this tool free and private to use?
- Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
- Do these tools replace medical guidance?
- No. These outputs are general fitness estimates — not medical advice.
- Can I switch between metric and imperial units?
- Yes. Every tool supports both systems and remembers your preference in localStorage.