What Is Ideal Body Weight?
Ideal body weight (IBW) is an estimate of the weight at which a person of a given height is considered to be at optimal health. The concept dates back to the 1960s, when clinicians needed a quick way to estimate appropriate medication doses for hospitalised patients — and has since been widely adopted in nutrition, fitness, and public health.
It is important to understand that "ideal weight" is not a precise target. No formula can account for individual differences in muscle mass, bone density, fat distribution, age, or ethnicity. The four formulas displayed here — Devine, Robinson, Miller, and Hamwi — each produce slightly different estimates, typically within 5–8 kg of each other. Use them as reference points, not goals to hit exactly.
The Four Formulas Explained
Each formula calculates ideal weight from height (in inches above 5 feet / 152 cm) and sex:
| Formula | Male (kg) | Female (kg) | Original Purpose |
|---|---|---|---|
| Devine (1974) | 50 + 2.3 × (in above 5ft) | 45.5 + 2.3 × (in above 5ft) | Drug dosing in hospitals |
| Robinson (1983) | 52 + 1.9 × (in above 5ft) | 49 + 1.7 × (in above 5ft) | Updated Devine estimate |
| Miller (1983) | 56.2 + 1.41 × (in above 5ft) | 53.1 + 1.36 × (in above 5ft) | Alternative clinical reference |
| Hamwi (1964) | 48.1 + 2.72 × (in above 5ft) | 45.4 + 2.27 × (in above 5ft) | Diabetes management |
None of these formulas were designed as standalone fitness goals — they were clinical tools. The most relevant modern reference is the BMI healthy range of 18.5–24.9, which provides a weight window rather than a single target.
BMI Range vs Formula Estimates
For most adults, the BMI healthy range is the most practical guide. Unlike the single-point estimates from Devine or Hamwi, the BMI range acknowledges that healthy weight exists on a spectrum. A 175 cm male, for example, has a healthy BMI range of approximately 56.7–76.3 kg — a span of nearly 20 kg. Being anywhere in this range is generally associated with lower cardiometabolic risk.
The limitation of BMI is that it does not account for body composition. A lean, muscular person at 78 kg and 175 cm has a BMI of 25.5 (slightly "overweight") but is almost certainly healthier than a sedentary person at 72 kg with the same height and high body fat. For a complete picture, use the Body Fat Calculator alongside this one.
Setting Realistic Weight Goals
Once you know your healthy weight range, you can set a meaningful target:
- Above the range: A gradual deficit of 300–500 kcal/day leads to 0.3–0.5 kg of fat loss per week. Use the TDEE Calculator to find your maintenance calories.
- Within the range: Focus on body composition rather than weight — building muscle while maintaining weight can improve health significantly.
- Below the range: Being underweight carries health risks including nutrient deficiencies and bone density loss. Consult a healthcare provider.
For a comprehensive understanding of body composition beyond weight, read the Body Composition Guide. To estimate your current body fat percentage, use the Body Fat Calculator or the Lean Body Mass Calculator.
Scientific References: Devine BJ. (1974). Gentamicin therapy. Drug Intelligence and Clinical Pharmacy. 8:650–655. — Robinson JD, et al. (1983). Determination of ideal body weight. American Journal of Hospital Pharmacy. 40(6):1016–1019. — World Health Organization. (2004). BMI Classification. Global Database on Body Mass Index.