Ask five different sources what your "ideal weight" should be, and you'll likely get five slightly different answers. That's not a flaw in any single formula — it's a reflection of the fact that human bodies vary enormously, and no single number can perfectly capture what's healthy for every individual. Still, ideal weight calculators remain useful as a general reference point, especially when you understand where the numbers come from and how to interpret them sensibly.
Most ideal weight formulas were developed decades ago, often by insurance companies or medical researchers trying to find weight ranges associated with lower mortality risk. The Devine formula, originally created in the 1970s to help dose medications accurately, is still one of the most commonly used today. Others, like the Robinson, Miller, and Hamwi formulas, were built around similar goals but with slightly different underlying datasets, which is why their outputs don't always match exactly.
Most of these formulas start with a baseline weight for a given height — typically 5 feet — and then add a fixed number of kilograms or pounds for every additional inch of height beyond that baseline. The constants differ slightly between men and women, since body composition and average frame size differ by sex on average. A calculator usually runs your height through several of these formulas at once and shows you the range they collectively suggest.
For a man who is 5 feet 10 inches tall, the Devine formula would suggest an ideal weight of around 72 kilograms, while the Robinson formula might suggest something closer to 74 kilograms. Neither number is "wrong" — they're simply two slightly different statistical estimates built from different research populations, which is exactly why most calculators show a range instead of a single figure.
None of these formulas account for muscle mass, bone density, or where fat is distributed on the body. A competitive swimmer or weightlifter will often weigh more than their "ideal" range suggests, simply because muscle is denser than fat. Athletic body types routinely fall outside these ranges while being perfectly healthy, which is why ideal weight numbers work best as a loose reference rather than a strict target.
Ideal weight calculators are commonly used in clinical settings to estimate medication dosages, since several drug dosing guidelines are based on ideal body weight rather than actual weight. Outside of medical contexts, they're a reasonable starting point for anyone setting a long-term weight goal, particularly if you're unsure what a healthy target even looks like for your height. They're less useful for athletes, older adults, or anyone with an atypical body composition, where the underlying assumptions behind the formulas don't hold up as well.
Which ideal weight formula is the most accurate? None of them is definitively "correct" — they're all statistical estimates from different research populations. That's why most calculators show a range from several formulas rather than a single definitive number.
Does frame size matter for ideal weight? Yes, though most basic formulas don't account for it directly. People with a larger bone structure naturally sit toward the higher end of the suggested range, while smaller-framed individuals tend to sit toward the lower end.
Why do I weigh more than my "ideal" weight but still look lean? Muscle is denser than fat, so athletic or muscular individuals often exceed their calculated ideal weight while carrying very little excess fat — a good example of why these formulas shouldn't be treated as strict targets.
Should I use ideal weight or BMI to track progress? Either can work as a general reference point, but tracking trends in your actual weight, waist measurement, or body fat percentage over time tends to be more useful than chasing an exact ideal weight number.
Rather than fixating on hitting an exact figure, use the calculated range as a general checkpoint alongside how you actually feel, perform, and look. Two people at the same height can have very different healthy weights depending on muscle mass, bone structure, and overall build, so treat this number as one input among several rather than a strict finish line.
Ideal weight calculators offer a helpful ballpark, not a medical verdict. They're most useful when combined with other measures and common sense about your own body type and lifestyle. Try our Ideal Weight Calculator to see where you fall across multiple established formulas at once.