Ideal Body Weight Explained: How the Devine, Robinson, Miller, and Hamwi Formulas Work
By the Super Simple Digital Tools Team · Updated June 2026
If you have ever wondered why one calculator says your ideal weight is 70 kg and another says 75 kg, the answer is that there is no single official formula. Four widely cited equations exist, each created by a different researcher at a different time, and each makes slightly different assumptions. This calculator runs all of them so you can see the spread rather than trusting one arbitrary number. Understanding where these formulas come from makes the results far easier to interpret.
The oldest is the Hamwi formula from 1964, originally a quick bedside rule: 106 pounds for the first 5 feet of height for men (100 for women), plus a few pounds per extra inch. The Devine formula followed in 1974 and became the standard in hospitals, mainly because it was used to calculate medication doses. Robinson and Miller, both published in 1983, refined the coefficients using newer data. Miller's version generally produces the highest estimates, which is why it often sits at the top of your results range.
To read your results, look at the range first, not any single value. If three of the four formulas cluster around the same figure and one sits a little higher or lower, the cluster is your best reference. The average the tool provides smooths out the differences. Then compare that band to how you actually feel, your energy, fitness, and any guidance from a healthcare professional. The number is a map reference, not the destination.
It helps to remember what these formulas were never meant to do. They do not measure body fat, they do not know whether your weight is muscle or fat, and they were not designed to define attractiveness or even health. A 1.8 metre powerlifter and a 1.8 metre sedentary person receive the identical ideal weight from every formula, even though their bodies are completely different. That is the built-in blind spot of any height-and-sex-only method.
So use the ideal weight calculator the way clinicians originally intended: as a fast, rough reference to orient yourself, set a sensible goal range, or sanity-check a target before discussing it with a professional. Pair it with other measures such as waist circumference, body-fat percentage, or simply how your clothes fit. Taken together, those signals tell a far richer story than any one formula can, and they keep you from chasing a number that was never the full picture.
- Treat the spread between the four formulas as your reference band, and use the average as a single ballpark figure.
- Enter height carefully in your preferred unit; even a one-inch difference shifts every result by roughly 1.4 to 2.3 kg.
- If you are muscular or athletic, expect to weigh above the calculated ideal and rely on body-fat measurement instead.
- Use the result as a starting target to discuss with a doctor or trainer, not as a fixed goal to chase on its own.