Ideal Body Weight Calculator
Compare 4 Validated Formulas — Devine, Robinson, Miller & Hamwi
What Is Ideal Body Weight?
Ideal Body Weight (IBW) is an estimated weight that is associated with optimal health outcomes for a given height. Unlike what the name might suggest, IBW does not represent a single “perfect” weight. Rather, it is a clinically derived estimate originally developed for use in medical dosing and physiological calculations.
Clinical Uses of IBW:
- Drug dosing: Many medications — especially aminoglycosides, anesthetics, and chemotherapy agents — are dosed based on ideal body weight rather than actual weight to avoid toxicity in obese patients.
- Tidal volume calculation: In mechanical ventilation, tidal volumes are set using predicted (ideal) body weight to prevent lung injury from overinflation.
- Nutritional assessment: IBW serves as a baseline reference when calculating caloric and protein needs in clinical nutrition.
- Body composition estimation: The difference between actual weight and IBW can help estimate excess body fat, though this is a rough approximation.
Important: IBW formulas were developed using insurance mortality data from the mid-20th century and have known limitations. They should not be interpreted as a personal weight goal without clinical context. A healthy weight range (based on BMI 18.5–24.9) provides a broader and more practical reference for most individuals.
The 4 Ideal Body Weight Formulas
Devine Formula (1974)
The most widely used IBW formula, originally published by Dr. B.J. Devine for use in calculating drug dosages. It was not derived from a formal study but became the de facto standard in clinical practice.
- Male: 50 kg + 2.3 kg for each inch over 5 feet
- Female: 45.5 kg + 2.3 kg for each inch over 5 feet
Most appropriate for: Drug dosing, ventilator settings, and general clinical reference. Remains the primary formula used in hospitals today.
Robinson Formula (1983)
Developed by Robinson, Prickett, and Piperno as a modification of the Devine formula, using updated Metropolitan Life Insurance Company data from 1983.
- Male: 52 kg + 1.9 kg for each inch over 5 feet
- Female: 49 kg + 1.7 kg for each inch over 5 feet
Most appropriate for: Alternative reference when a less aggressive weight-for-height estimate is preferred; tends to produce slightly higher values for shorter women.
Miller Formula (1983)
Published by Miller et al. in the same year as the Robinson formula, also based on actuarial data. It generally produces higher estimates than the other formulas.
- Male: 56.2 kg + 1.41 kg for each inch over 5 feet
- Female: 53.1 kg + 1.36 kg for each inch over 5 feet
Most appropriate for: Providing an upper-range IBW estimate; may be more suitable for individuals with larger frame sizes.
Hamwi Formula (1964)
The oldest of the four, developed by Dr. G.J. Hamwi for use in nutritional assessment and diabetes management. Published as a quick estimation method.
- Male: 48 kg + 2.7 kg for each inch over 5 feet
- Female: 45.5 kg + 2.2 kg for each inch over 5 feet
Most appropriate for: Nutritional counseling and diabetes dietary planning. Often used as a quick bedside calculation by dietitians.
Limitations of Ideal Body Weight Formulas
While IBW formulas remain useful in specific clinical contexts, they have significant limitations that should be understood:
- Body composition ignored: IBW formulas do not distinguish between lean mass (muscle, bone) and fat mass. A highly muscular person may exceed their IBW while having a healthy body fat percentage.
- Frame size not considered: Individuals naturally vary in skeletal frame size (small, medium, large). Someone with a large frame may have a higher healthy weight than the formula predicts.
- Age not factored: Body composition changes with age. These formulas produce the same result for a 25-year-old and a 65-year-old of the same height and sex.
- Ethnicity and population differences: The original data were derived predominantly from Caucasian populations in the United States. They may not be equally applicable across all ethnic groups.
- Historical data: The underlying actuarial data are from the 1950s through 1980s and may not reflect current understanding of the relationship between weight and health outcomes.
- Height baseline limitation: All four formulas use a baseline of 5 feet (60 inches). They become less reliable for individuals significantly shorter or taller than average.
A BMI-based healthy weight range (18.5–24.9 kg/m²) is generally more appropriate than any single IBW formula for determining a personal weight goal. For the most comprehensive assessment, consider combining BMI with waist circumference, body fat percentage, and overall metabolic health markers.
Understanding Healthy Weight Ranges
Rather than targeting a single “ideal” number, health professionals increasingly recommend focusing on a healthy weight range based on multiple indicators:
BMI-Based Weight Range
The World Health Organization defines a healthy BMI as 18.5–24.9 kg/m². This calculator shows the corresponding weight range for your height. The BMI range accounts for natural variation in body types and is a more flexible target than a single IBW number.
Waist Circumference
Central (abdominal) fat is more strongly associated with metabolic disease risk than overall weight. The WHO recommends:
- Men: Waist circumference below 94 cm (37 in); increased risk above 102 cm (40 in)
- Women: Waist circumference below 80 cm (31.5 in); increased risk above 88 cm (34.6 in)
Body Composition
Body fat percentage provides a more accurate picture of health than weight alone. Healthy ranges are generally:
- Men: 10–20% body fat (athletes: 6–13%)
- Women: 18–28% body fat (athletes: 14–20%)
The Big Picture
No single measurement tells the full story. A comprehensive assessment considers BMI, waist circumference, body composition, blood pressure, blood sugar, lipid levels, fitness level, and family history. Work with your healthcare provider to determine the weight range that is healthiest for you as an individual.
Frequently Asked Questions
Ideal body weight (IBW) is a clinically estimated weight for a given height that was originally developed for use in medical calculations such as drug dosing and ventilator settings. It is calculated using formulas that take into account height and sex. The four most commonly used formulas — Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) — all use a baseline weight at 5 feet tall, plus an incremental amount for each additional inch of height. Each formula was derived from different sources of actuarial and clinical data, which is why they produce slightly different results.
No single formula is definitively more “accurate” than the others because they were developed for different purposes and from different data sets. The Devine formula is the most widely used in clinical practice, particularly for drug dosing and ventilator management. A 2000 review by Pai and Paloucek in the journal Annals of Pharmacotherapy found that all four formulas have similar limitations and that no single equation consistently outperforms the others. For a practical personal reference, looking at the average of all four or the healthy BMI weight range may be the most useful approach.
All four IBW formulas use 5 feet (60 inches) as a baseline, adding weight for each inch above that threshold. For heights below 5 feet, the formulas subtract weight, which can produce unreliable or clinically meaningless results at very short statures. A minimum of 4’10” (58 inches) is enforced as a practical lower limit where the formulas still produce reasonable estimates. For individuals shorter than this, a BMI-based weight range is a more appropriate reference.
Not necessarily. IBW is a mathematical estimate, not a personalized health target. Your healthiest weight depends on many factors that these formulas do not consider, including your body composition (muscle vs. fat), frame size, age, fitness level, metabolic health, and medical history. A person who is muscular may weigh significantly more than their IBW while being in excellent health. For most people, a healthy BMI range (18.5–24.9) combined with a normal waist circumference and good metabolic markers provides a better indication of healthy weight than any single formula.
Each formula was developed independently using different data sources, populations, and methodologies. The Devine formula (1974) was based on clinical observation, Hamwi (1964) on nutritional assessment data, and both Robinson and Miller (1983) on Metropolitan Life Insurance actuarial tables from different years. They also use different increment values per inch above 5 feet. The divergence between results tends to increase with height — for taller individuals, the spread between the highest and lowest formula estimate can be quite substantial. This variation illustrates why no single number should be treated as a definitive target.
The healthy BMI weight range is calculated using the standard BMI formula: BMI = weight (kg) / height (m)². For a given height, we solve for weight at both ends of the healthy BMI range (18.5 and 24.9). For example, for someone who is 5’10” (1.778 m), the healthy weight range is: Low end = 18.5 × 1.778² = 58.5 kg (129 lbs), High end = 24.9 × 1.778² = 78.7 kg (173 lbs). This range accounts for natural variation in body types and is recommended by the WHO as a general guideline, though it also has limitations for highly muscular individuals and certain populations.
Medical Disclaimer
This Ideal Body Weight Calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Ideal body weight formulas are clinical estimation tools with known limitations — they do not account for body composition, frame size, age, ethnicity, or individual health factors. Your results should not be used as a personal weight goal without consulting a qualified healthcare professional. For clinical drug dosing, ventilator settings, or nutritional planning, always defer to your healthcare provider’s judgment. All calculations are performed in your browser — no personal data is stored on our servers or shared with any third party.
References
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650–655.
- Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm. 1983;40(6):1016–1019.
- Miller DR, Carlson JD, Lloyd BJ, Day BJ. Determining ideal body weight (and dosing errors with aminoglycoside therapy). Am J Hosp Pharm. 1983;40(6):1016.
- Hamwi GJ. Therapy: changing dietary concepts. In: Danowski TS, ed. Diabetes Mellitus: Diagnosis and Treatment. Vol 1. New York: American Diabetes Association; 1964:73–78.
- Pai MP, Paloucek FP. The origin of the “ideal” body weight equations. Ann Pharmacother. 2000;34(9):1066–1069.