Calculate your ideal body weight using four widely recognised clinical formulas — Robinson (1983), Miller (1983), Devine (1974), and Hamwi (1964) — as well as the healthy BMI weight range. Enter your height, age, and gender in imperial or metric units to see your personalised ideal weight range with complete step-by-step working.
Ideal Weight Calculator
IBW Formula Reference
| Formula | Male Base | Female Base | Per Inch Over 5 ft |
|---|---|---|---|
| Hamwi (1964) | 48.0 kg | 45.5 kg | +2.7 kg (M) / +2.2 kg (F) |
| Devine (1974) | 50.0 kg | 45.5 kg | +2.3 kg (M & F) |
| Robinson (1983) | 52.0 kg | 49.0 kg | +1.9 kg (M) / +1.7 kg (F) |
| Miller (1983) | 56.2 kg | 53.1 kg | +1.41 kg (M) / +1.36 kg (F) |
Healthy BMI Weight Range Reference
| BMI Classification | BMI Range | Health Status |
|---|---|---|
| Underweight | < 18.5 | Below healthy range |
| Normal Weight | 18.5 – 24.9 | Healthy range |
| Overweight | 25.0 – 29.9 | Above healthy range |
| Obese | ≥ 30.0 | High health risk |
What is Ideal Body Weight?
Ideal body weight (IBW) is a clinical estimate of how much a person should weigh based on their height and gender. The concept was originally developed not for aesthetic purposes, but as a practical tool for calculating medication dosages in medical settings — particularly for drugs whose metabolism is more closely linked to lean body mass than to total body weight. Over time, IBW has also been adopted in fitness, nutrition, and general health guidance as a useful reference point.
It is important to understand that no single IBW formula is perfectly accurate for every individual. These formulas were developed based on population averages and do not account for differences in body composition, bone density, muscle mass, or ethnic background. A person who is muscular and lean may appear “overweight” by IBW standards, while a sedentary person within the IBW range may still carry excess body fat. IBW is a guideline, not a definitive target.
The Four Major IBW Formulas
All four formulas follow the same basic structure: a base weight is assigned for a person who is exactly 5 feet tall (152.4 cm), and an additional fixed amount is added for each inch of height over 5 feet. The formulas differ in their base values and per-inch increments, reflecting the different research populations and methodologies used by each author.
The Devine formula (1974) is the most widely used in clinical medicine and is the standard in most pharmacokinetic calculations. The Hamwi formula (1964) was developed earlier and uses slightly higher per-inch increments, particularly for men. The Robinson (1983) and Miller (1983) formulas are modifications of Devine, and both tend to produce results that are similar in range, though Miller’s formula gives somewhat higher base weights.
Healthy BMI Weight Range
In addition to the four formula-based IBW estimates, this calculator shows the weight range corresponding to a healthy BMI of 18.5 to 24.9, as defined by the World Health Organization (WHO). BMI (Body Mass Index) is calculated as weight in kilograms divided by height in metres squared. Although BMI has well-known limitations — particularly its inability to distinguish between fat and muscle — the healthy BMI range remains a widely used reference for population-level health assessments.
Factors That Affect Your Ideal Weight
Age: Most IBW formulas are designed for adults. As people age, muscle mass tends to decrease and body fat tends to accumulate, even when total body weight stays the same. Maintaining strength through resistance exercise and adequate protein intake can help preserve lean mass as you get older.
Gender: Males and females have different baseline body compositions. Women naturally carry a higher percentage of body fat, while men typically have more muscle mass and denser bones. This is why the IBW formulas use different base values for men and women.
Body Frame Size: People with larger bone structures naturally weigh more. Body frame size is commonly estimated by measuring wrist circumference relative to height. A large-framed person may healthily exceed the standard IBW, while a small-framed person may fall below it.
Limitations
The IBW formulas were not designed to account for variations in body composition, physical fitness, ethnicity, or medical conditions. They are best used as rough reference points alongside other measures such as body fat percentage and waist circumference. If you have specific health goals or medical concerns, consult a qualified healthcare provider or registered dietitian for personalised guidance.
The information provided by this calculator is for general educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.