Where these formulas come from
The four clinical ideal weight formulas were not designed as fitness goals — they were developed for medical drug dosing. Many medications are dosed by lean body mass rather than total weight to avoid toxicity in patients carrying excess fat. Because lean mass cannot be directly measured at the bedside, clinicians needed a quick height-based estimate.
Benjamin Devine published the first widely adopted formula in 1974, based on a small sample, and it quickly became the default in pharmacokinetics textbooks. Robinson (1983) and Miller (1983) each proposed modifications after analysing slightly larger datasets and finding Devine overestimated ideal weight at taller heights. Hamwi (1964) is the oldest, originally developed for nutritional assessment in hospitalised patients. All four remain in clinical use today primarily because they are fast to compute from a patient's height alone.
The BMI-based healthy weight range
The World Health Organization defines a healthy BMI as 18.5–24.9 kg/m². The corresponding weight range for any height is calculated by solving BMI = weight ÷ height² for weight at each boundary. This range is broader than the clinical formulas and is grounded in large epidemiological studies linking BMI to all-cause mortality and chronic disease risk.
Because BMI does not account for body composition, the upper end of the healthy range (24.9) can be attained by a very muscular person with low body fat, while a sedentary person at BMI 22 may carry clinically significant visceral fat. Use the BMI range as a broad population reference rather than a personal precision target.
What the formulas cannot tell you
All five methods share the same fundamental limitation: they are based solely on height and sex. They ignore:
- •Body composition. Muscle weighs more than fat. A bodybuilder and an untrained person of the same height can have the same ideal weight by formula, but very different health profiles.
- •Age. Muscle mass naturally declines with age (sarcopenia), so the same body weight at 60 involves more fat and less muscle than at 30.
- •Ethnicity and frame size. East and South Asian populations face elevated metabolic risk at lower BMI values. Larger skeletal frames can support more lean mass at any given height.
- •Fat distribution. Central adiposity (waist fat) carries higher cardiovascular risk than the same weight distributed in peripheral fat. No weight formula captures this; waist circumference and waist-to-height ratio are better proxies.
A practical approach to using these numbers
Treat the average of the four formulas as a starting reference, not a prescription. If your current weight falls within the BMI-based healthy range and you have healthy body composition, normal blood pressure, and good energy levels, you likely do not need to change your weight at all. If you are meaningfully above or below these figures, use them as a directional guide alongside other markers — body fat percentage, waist circumference, fitness metrics, and blood work — when setting health or fitness goals with a clinician or qualified nutritionist.
Frequently asked questions
Which ideal weight formula is most accurate?▾
No single formula is universally most accurate — they were all developed for specific clinical contexts such as drug dosing. The Devine formula is the most widely cited in pharmacokinetics. The BMI-based range (18.5–24.9 kg/m²) is the WHO reference and accounts only for height, not frame size or muscle mass. Using the average of multiple formulas gives a reasonable reference range.
Why do the formulas give different results?▾
Each formula was derived from a different dataset and era. Devine (1974) was based on a small clinical sample used for drug dosing calculations. Robinson (1983) and Miller (1983) were developed as refinements using slightly different populations. Hamwi (1964) is the oldest and produces the widest variation at extreme heights.
Does ideal weight account for muscle mass?▾
No — all four clinical formulas and the BMI-based range are based solely on height and sex. They cannot distinguish between fat mass and muscle mass. A heavily muscled athlete will appear 'overweight' by these standards despite very low body fat. Consider body fat percentage as a complementary metric.
What is the BMI-based weight range?▾
The BMI-based range shows the body weights that correspond to a BMI of 18.5 to 24.9 at your height — the World Health Organization's definition of a healthy weight. This is the most widely used population reference and is based on large-scale epidemiological data linking BMI to health outcomes.
Is ideal weight different for men and women of the same height?▾
Yes. All four clinical formulas produce lower ideal weight estimates for women than men at the same height, reflecting average differences in frame size and lean mass between sexes. The typical difference ranges from 4.5 to 6 kg depending on the formula and height.
Should I try to reach my ideal weight?▾
These figures are reference ranges, not targets you must achieve. Health is influenced by many factors beyond weight: physical fitness, blood markers, sleep, stress, and genetics all matter. A sustainable weight that you can maintain while feeling energetic and healthy is more meaningful than hitting a formula's output.
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.
- •Miller DR, et al. (1983). Ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy, 40(1), 107–110.
- •Hamwi GJ. (1964). Changing dietary concepts. In: Danowski TS, ed. Diabetes Mellitus: Diagnosis and Treatment. New York: American Diabetes Association.
- •World Health Organization. (2000). Obesity: Preventing and Managing the Global Epidemic. WHO Technical Report Series 894.