Four formulas, one shape
All four classic ideal weight formulas work the same way. They start with a weight at exactly 5 feet and add a fixed amount for every inch above it. Only the numbers change.
That shared shape matters. Because each formula adds the same amount per inch no matter how tall you are, they drift apart as height goes up. A formula with a low base and a steep slope, like Hamwi for men, starts below the others and ends above them.
All four give kilograms. For pounds, multiply by about 2.2046. Devine's 73.0 kg for a man who is 5 feet 10 inches tall works out to about 160.9 lb, and Hamwi's 75.0 kg to about 165.3 lb.
Where each one came from
Hamwi is the oldest. A 2021 review of ideal body weight notes that no method of development was ever reported for it. Devine followed in 1974, and the same review says it relied on observation rather than statistics.
Robinson and Miller are the only two built with regression. Both published in 1983, fitting their equations to height and weight table data. Miller's team also subtracted a few pounds to account for clothing. None of the four came from studies of which weight is healthiest.
How far apart they land
At 5 feet 10 inches with the male coefficients, the four formulas give 70.3 kg (Miller), 71.0 (Robinson), 73.0 (Devine) and 75.0 (Hamwi). That's a 4.7 kg gap, about 10 lb, from the same height.
At 5 feet 5 inches with the female coefficients, they cluster more tightly: 56.5 (Hamwi), 57.0 (Devine), 57.5 (Robinson) and 59.9 kg (Miller). Shorter heights mean fewer inches over 5 feet, so the slopes have less room to spread the answers. Note the order changes too. Miller is lowest for the tall man and highest for the shorter woman.
How they compare with BMI
BMI takes a different route. It multiplies a BMI by height squared, so the weight added per inch grows as you get taller instead of staying fixed. At 5 feet 10 inches, a BMI of 22 works out to about 69.5 kg, close to Miller. The full CDC healthy range of 18.5 to under 25 runs from about 58.5 to 79.0 kg.
The formulas give you a point. BMI gives you a range about four times wider. For most everyday questions about a healthy weight, the range is the more honest answer.
Which one should you use?
If a textbook, worksheet or clinic names a specific formula, use that one so your numbers match theirs. Devine became the most widely used. Some drug-dosing methods call for an ideal body weight, and a pharmacist or prescriber decides when that applies.
For your own sense of a healthy weight, don't pick one formula and treat it as a target. Look at the spread and the BMI range together. Our ideal weight calculator shows all four formulas and the BMI range for your height on one screen, so you can see how much they agree.
Remember what none of them can see: muscle, frame, age, health and how you feel. If you're thinking about changing your weight, a doctor or registered dietitian can help you set a goal that fits you.
Frequently asked questions
Why is Hamwi so different for tall men?
It has the steepest slope for men, 2.7 kg per inch. That adds up fast, so it pulls ahead of the other three at taller heights.
Is the Robinson formula better than Devine?
Robinson was built with regression on table data, while Devine relied on observation. That makes Robinson's method more documented, but neither one measures health.
Should I average the four formulas?
You can, but it isn't more accurate. The formulas share a similar shape and related data, so their average just sits in the middle of the same assumptions.
Why do the formulas start at 5 feet?
That's how they were written: a base weight at 5 feet plus an amount per inch above it. Using them for shorter heights means extending them beyond their design.
References
These sources support the method or guidance used for Ideal Weight Calculator. Verify time-sensitive rules at the source.
Try the calculator
Open Ideal Weight Calculator, enter your scenario, and compare its supporting rows with this guide's method and checks.