Ideal Weight Calculator
See your estimated ideal body weight from four classic medical formulas, based on height and sex.
| Devine formula | 0 lb |
| Robinson formula | 0 lb |
| Miller formula | 0 lb |
| Hamwi formula | 0 lb |
Ideal Weight Calculator: Formula, Worked Examples & Complete Guide
Written by Magesh | Financial Tools & Calculation Specialist · Last updated July 31, 2026
In two sentences: An ideal weight calculator estimates a healthy weight range using clinically-recognized formulas like Devine, Robinson, Miller, and Hamwi, all built on the same basic structure — a baseline weight at 5 feet of height, plus an increment for every additional inch. This guide breaks down all four formulas, worked examples showing how they diverge for the same person, and why the spread between them matters more than any single number.
What Is an Ideal Weight Calculator?
An ideal weight calculator estimates a reference body weight based on height and sex, using formulas originally developed for medical purposes like drug dosing rather than as a personal fitness target. Because several different formulas exist, an ideal weight calculator typically shows results from multiple methods side by side rather than a single definitive number.
The Ideal Weight Calculator Formulas
All four major formulas share the same structure: a baseline weight for 60 inches (5 feet) of height, plus a fixed amount added per inch above that.
Devine (1974):
Men: IBW = 50.0 kg + 2.3 kg × (height in inches − 60)
Women: IBW = 45.5 kg + 2.3 kg × (height in inches − 60)
Robinson (1983):
Men: IBW = 52.0 kg + 1.9 kg × (height in inches − 60)
Women: IBW = 49.0 kg + 1.7 kg × (height in inches − 60)
Miller (1983):
Men: IBW = 56.2 kg + 1.41 kg × (height in inches − 60)
Women: IBW = 53.1 kg + 1.36 kg × (height in inches − 60)
Hamwi (1964):
Men: IBW = 48.0 kg + 2.7 kg × (height in inches − 60)
Women: IBW = 45.5 kg + 2.2 kg × (height in inches − 60)
Worked Examples
Example 1: A 5’10” (70-inch) man across all four formulas
Height above 60 inches = 70 − 60 = 10 inches
Devine: 50.0 + (2.3 × 10) = 73.0 kg (~161 lbs)
Robinson: 52.0 + (1.9 × 10) = 71.0 kg (~157 lbs)
Miller: 56.2 + (1.41 × 10) = 70.3 kg (~155 lbs)
Hamwi: 48.0 + (2.7 × 10) = 75.0 kg (~165 lbs)
Example 2: A 5’5″ (65-inch) woman across all four formulas
Height above 60 inches = 65 − 60 = 5 inches
Devine: 45.5 + (2.3 × 5) = 57.0 kg (~126 lbs)
Robinson: 49.0 + (1.7 × 5) = 57.5 kg (~127 lbs)
Miller: 53.1 + (1.36 × 5) = 59.9 kg (~132 lbs)
Hamwi: 45.5 + (2.2 × 5) = 56.5 kg (~125 lbs)
Example 3: Understanding the spread between formulas
For the 5’10” man in Example 1, the four formulas span from 70.3 kg (Miller) to 75.0 kg (Hamwi) — a range of about 4.7 kg (10.4 lbs). This spread is the honest headline of any ideal weight calculator: there is no single scientifically “correct” answer, only a reasonable range depending on which historical formula and population data set is used as the reference.
Example 4: Cross-checking against a BMI-based range
The World Health Organization’s healthy BMI range (18.5–24.9 kg/m²) offers an alternative reference point. For someone 170 cm tall, that BMI range translates to roughly 53.5 kg to 72.0 kg — a much wider window (nearly 19 kg) than any single IBW formula produces, since it doesn’t rely on a single fixed multiplier and instead reflects a broader range of body types considered healthy.
Step-by-Step: How to Use an Ideal Weight Calculator
- Enter your height (in feet/inches or centimeters) and sex.
- Review results from multiple formulas — Devine, Robinson, Miller, and Hamwi — rather than fixating on just one.
- Compare the resulting range against a BMI-based healthy weight window for additional context.
- Treat the output as a general reference point, not a rigid personal target, since none of the formulas account for muscle mass, bone density, or individual body composition.
- If you’re using the result for a specific medical purpose (like dosing), confirm with a healthcare provider which formula is standard for that particular application.
Why the Formulas Differ: A Brief History
The Devine formula, published in 1974, was originally developed for calculating gentamicin antibiotic dosages and was not based on large-scale population data — it became the default clinical standard largely through adoption in pharmacy practice, not because it was proven more biologically accurate than the alternatives. The Robinson formula (1983) refined this approach using mortality statistics from Metropolitan Life Insurance tables, producing more conservative estimates for taller individuals. The Miller formula, published the same year, uses a higher baseline weight but a lower per-inch increment, converging with the other formulas at greater heights. The Hamwi formula, the oldest of the four (1964), was developed for diabetes management and nutrition counseling and uses the highest per-inch multiplier for men of any of the four methods.
What an Ideal Weight Calculator Doesn’t Account For
None of these formulas account for lean muscle mass, bone density, ethnic variation in body composition, or individual health goals. A competitive athlete and a sedentary office worker of identical height can both be perfectly healthy at meaningfully different weights, despite an ideal weight calculator producing the same reference number for both. These formulas were built decades ago primarily to standardize medication dosing calculations, not to define a universal personal weight target — treating the output as a strict goal rather than a general reference point is a common misuse of the tool.
Interpreting Your Ideal Weight Calculator Results Sensibly
An ideal weight calculator is most useful when you read the full spread across formulas rather than fixating on a single output number, since that spread itself is the most honest piece of information the tool provides.
How to use an ideal weight calculator responsibly
- Look at the range, not just one formula’s result. As shown in the worked examples above, a several-kilogram gap between formulas is completely normal, and treating any single number as a precise target misrepresents what these formulas were built to do.
- Cross-reference against a BMI-based healthy range for a second, independent perspective, since BMI and IBW formulas were developed through different methods and rarely align perfectly.
- Factor in your own body composition context, especially if you carry more muscle mass than average — an ideal weight calculator has no way to distinguish muscle from fat, so athletes and highly active individuals often sit above the calculated range while remaining perfectly healthy.
- Use the result as a conversation starter with a healthcare provider, particularly if the number is being used for a clinical purpose like medication dosing, rather than as a self-directed weight-loss or weight-gain target.
Frequently Asked Questions
None is definitively “most accurate” for general health purposes — each was developed using different reference populations and for different original purposes (mostly medication dosing). The Devine formula remains most common in clinical settings simply because it became the standardized default in pharmacy practice.
Each formula was developed independently, using different baseline weights and per-inch multipliers derived from different historical data sets, so there’s no single unified source they all draw from.
Treat it as a general reference point rather than a strict target. Muscle mass, frame size, and individual health factors all affect what a genuinely healthy weight looks like for any specific person, well beyond what a height-and-sex-only formula can capture.
Ideal body weight (IBW) formulas produce a single reference weight based on height and sex. BMI (Body Mass Index) instead produces a ratio of weight to height squared, and is typically used to define a healthy weight range rather than a single number.
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In summary, an ideal weight calculator gives you a useful reference range rather than a single definitive number, and understanding why the Devine, Robinson, Miller, and Hamwi formulas diverge helps you interpret any individual result with appropriate context rather than treating it as a fixed personal target.
About the author: Magesh is a Financial Tools & Calculation Specialist focused on building and fact-checking online calculators across health, wellness, and everyday measurement topics.
Note: This calculator and article are provided for general educational and informational purposes only and do not constitute medical advice. Ideal body weight formulas are estimates originally developed for clinical dosing purposes and do not account for individual body composition. Consult a healthcare provider for personalized weight and health guidance.