How ideal weight calculators actually work, the difference between the major formulas, and why body type (somatotype) and frame size change what "ideal" really means for you.
Several formulas exist for estimating "ideal" body weight, all developed decades ago primarily for medical dosing calculations rather than as a personal fitness target. The most common include the Devine, Robinson, and Hamwi formulas — each uses height and sex as the main inputs, with slightly different base weights and adjustments per centimetre of height above a reference point.
These formulas produce a single number, but it's important to understand what that number actually represents: a population-level statistical estimate, not a precise individual target. Real healthy weight varies meaningfully around these figures based on muscle mass, frame size, and individual body composition.
Get an estimate using multiple recognised formulas, side by side.
Open Ideal Weight Calculator →Two people of identical height can have genuinely different healthy weights due to differences in bone structure and frame size. Someone with a naturally larger frame (broader shoulders, larger bone structure) will carry healthy weight at the higher end of any formula's range, while someone with a smaller frame may be perfectly healthy at the lower end — at the exact same height.
This is one of the clearest illustrations of why ideal weight calculators give a useful starting estimate rather than a definitive target — the same way BMI gives a starting point rather than a complete diagnosis.
Body typing (somatotype theory) categorises natural body tendencies into three broad types. Most people are a blend rather than a pure single type, but the framework is a useful way to understand why identical training and diet can produce different results for different people:
| Type | Natural Tendency | Common Characteristics |
|---|---|---|
| Ectomorph | Naturally lean | Narrow frame, fast metabolism, finds it harder to gain weight/muscle |
| Mesomorph | Naturally muscular | Athletic build, gains muscle relatively easily, moderate frame |
| Endomorph | Naturally higher body fat | Wider frame, gains weight more easily, often strong baseline strength |
Get an estimate of your natural body type tendency to better understand your training and nutrition response.
Open Body Type Calculator →The most useful way to apply ideal weight and body type information is as context rather than as a rigid target: