Where these formulas actually come from
None of the four numbers on this page were built to judge how anyone looks. Each began as a fast, bedside way to estimate a patient's lean body weight from height and sex alone, usually to answer a dosing question rather than an appearance one. That history changes what the number is actually for.
The most quoted of the four is Devine's, published in 1974 as a quick method for dosing gentamicin, an antibiotic that turns dangerous quickly if the dose comes from full body weight instead of something closer to lean mass, since fat tissue barely changes how a drug is cleared. Devine's formula solved that in seconds with a height measurement and nothing else. Robinson and Miller, both from 1983, adjusted the same shape of formula against different actuarial weight tables. Hamwi, the oldest of the four at 1964, served the same quick-estimate role in diabetes clinics. None of them were built by asking what a healthy body should weigh.
Why the four disagree
Put the same height and sex through all four and you will get four different answers, typically three to five kilograms apart from lowest to highest. That gap is not a sign that one formula is broken and the rest are correct. They were fitted to different data, for different clinical questions, across twenty years, so disagreement is the expected outcome, not an error.
Miller tends to sit toward the top of the four; Devine and Hamwi usually sit lower; Robinson often lands in between, though the ordering means little. The useful way to read four disagreeing numbers is to stop hunting for the single correct one and read the spread itself: the distance between the lowest and highest formula describes your ideal weight better than any figure pulled from the middle. This page leads with the average because that is what most people search for, but the table and bars below it matter more.
The healthy BMI range: a better modern anchor
A steadier anchor than any single named formula is the healthy BMI range for your height, 18.5 to 24.9 kilograms per metre squared. It is not perfect either, but it comes from very large modern population data linking body size to health outcomes, rather than from a handful of dosing calculations, and its width is an honest admission that health covers a range rather than one point. The BMI Calculator covers what that scale gets right and where it still falls short, including who it works least well for. On this page, that range sits beside the four formulas as the modern sanity check: when the formula average and the healthy BMI range broadly agree, that overlap is worth more than any one number by itself.
Frame size and muscle, honestly
Every formula here assumes something about you it never actually asks: an average skeletal frame and an average amount of muscle for your height. A prop forward or a competitive powerlifter can sit twenty kilograms above every formula on this page while carrying very little of it as harmful fat, and a formula built from population averages cannot tell that apart from the same weight carried as fat around the middle. A tape measure and a mirror get you closer than any number above.
Wrist-circumference adjustments exist to correct for frame size, scaling a result up or down for a small, medium or large skeleton. In practice they move the number by only a few percent, smaller than the gap the four formulas already show between themselves. If your build is visibly bigger or more muscular than average, trust your waist measurement over any frame-adjusted figure.
What "ideal" should mean in practice
Treat none of the four numbers, or their average, as a target to hit by a set date. A more useful question is what weight you can hold using habits you do not resent: eating you could keep up for years, activity that fits inside a normal week instead of fighting it, sleep that is not the first thing sacrificed when life gets busy. That weight usually sits somewhere inside the zone this page draws for you, not pinned to the average to the nearest kilogram.
Where you do want to move your weight towards that zone on purpose, the Calorie Deficit Calculator turns a target weight and a timeframe into a daily calorie number and a pace that will not fight the habits you are trying to build.
Questions people ask
Which of these four formulas is the most accurate?
None of them, in the sense most people mean by accurate. They were built to answer clinical dosing and actuarial questions, not to define one correct bodyweight, so asking which is right applies the wrong test. Devine has the strongest foothold in modern medicine, since hospitals still use it for drug dosing, but that is not the same as being right for you. Read all four as a spread, not a competition.
What is the ideal weight for a 5 ft 4 in woman?
Run 5 ft 4 in (162 cm) through all four formulas and you get four different answers: Devine 54.7 kg (120.6 lb), Robinson 55.8 kg (123.0 lb), Miller 58.5 kg (129.1 lb) and Hamwi 54.3 kg (119.7 lb). That is a spread of about 4.2 kg, or 9 lb, for one identical height and sex, which is exactly the point this page keeps making. The zone from lowest to highest tells you more than any single result plucked out of it.
Does age change your ideal weight?
Not in any of these four formulas; each one runs on height and sex alone, with no age term in the maths. That is a genuine limitation, because body composition shifts with age even when the scale does not. Most adults lose muscle and gain fat through their forties, fifties and sixties, so an identical weight at 25 and 65 can describe two different bodies. A body-fat or waist measurement tracks that shift better than any weight formula.
Should I diet down to the exact formula number?
No. Treat it as the middle of a plausible zone rather than a finish line to cross exactly. Let how your clothes fit, your energy and a body-fat trend measured over months guide when to stop, with the formula average sitting in the background rather than driving the decision. Ending a diet a few kilograms either side of the number, because your body is telling you to, is a better call than chasing a formula to the decimal place.
These formulas estimate lean body weight for healthy adults from published equations; none of them is a medical assessment. Pregnancy, growing children, and unusually muscular or unusually short adults all sit outside what they were built to measure.