Where these formulas came from
All four take a single input — your height — and were built for clinical convenience rather than for personal goal-setting. Hamwi (1964) came out of diabetes work. Devine (1974) was written to standardise drug dosing, and is still used that way. Robinson and Miller (both 1983) refitted the same shape of equation to newer population data.
Not one of them was designed to answer the question people bring to them. That is the reason this page shows all four and the gap between them, rather than picking the friendliest number and presenting it as a target.
What they cannot see
Two people, same height, same “ideal” weight
One trains four times a week and carries 12% body fat. The other has not trained in a decade and carries 30%. Every formula on this page returns the same number for both, and a BMI calculator puts them in the same category. The thing that differs between them — what the weight is made of — is invisible to all of it.
Frame size, limb proportions and training history all move the sensible answer by several kilos, and none of them is an input. This is also why muscular people are so routinely classified as overweight by BMI: the measure has no way to ask why the weight is there.
What to use instead
A goal weight is genuinely useful early, when there is a lot to lose and nearly all of it is fat. It gets less useful the closer you get, because the last stretch is a composition question rather than a mass question. At that stage a tape measure around the waist, a body fat estimate, and whether the weight on the bar is still going up will each tell you more than the scale.
Dietly is built on that premise: a weekly photo scored out of 100 across definition, leanness, symmetry, posture, body fat and potential, with the weak point named and a week of training built to fix it. The target is a shape, and the scale is one input among several rather than the verdict.
Common questions
- What is my ideal body weight?
- There is no single correct answer, and the four formulas on this page will give you four different ones from the same height — often 8 kg apart. They were built as clinical heuristics, largely for drug dosing and actuarial tables, from height alone. A healthy weight range from BMI is a more defensible reference point, and body composition is more informative than either.
- Why do the formulas disagree?
- Because they were derived at different times from different populations for different purposes. Hamwi (1964) came out of diabetes dosing, Devine (1974) out of drug clearance calculations, and Robinson and Miller (both 1983) were revisions fitted to newer data. None was designed to tell an individual what to weigh.
- Is BMI a better measure?
- Slightly, and only because it gives a range rather than a point. BMI still cannot distinguish muscle from fat, which is why trained people routinely read as overweight on it. Use the range for context, not as a target, and pay more attention to waist measurement and body fat percentage.
- Should I aim for a goal weight at all?
- A goal weight is a useful proxy early on, when there is a lot to lose and almost all of it will be fat. It becomes misleading as you get closer, because the last stretch is about what the remaining weight is made of. At that point progress photos, tape measurements and strength in the gym all tell you more than the scale does.