Four formulas, one height
There isn’t a single “ideal weight.” There are at least four competing formulas, and they disagree by a few kilos. So this tool runs all of them, Devine, Robinson, Miller, and Hamwi, off the same height and shows you the spread instead of pretending one answer is the truth.
You give it your height and sex. It hands back four numbers and their average. Underneath, it also draws the healthy BMI weight range for that height, the band between BMI 18.5 and 24.9, which is a more modern, range-based way to think about the same question.
Where these numbers come from
All four formulas share a structure: pick a base weight at 5 feet tall, then add a fixed amount for every inch above that. They differ in the constants:
- Devine (1974) was built for drug dosing, not aesthetics. It’s the one hospitals reach for. Men start at 50 kg, women at 45.5 kg, plus 2.3 kg per inch over 5 ft.
- Robinson (1983) trimmed Devine’s numbers down a little.
- Miller (1983) runs slightly higher than Robinson, with a gentler per-inch slope.
- Hamwi (1964) is the oldest, originally written in pounds for diabetes care. It tends to read on the higher end.
Because they all anchor at 5 ft, they get less reliable at the extremes. A very short or very tall person stretches assumptions that were fit to average adults.
Read it as a range, not a target
Here’s the honest part. None of these were designed to be your goal weight. Devine exists so a nurse can calculate a medication dose. The others are population shorthands from the 60s through 80s, and every one of them ignores frame size, muscle mass, body composition, and age. A stocky, muscular person will sit “over” all four and be perfectly healthy.
That’s exactly why the healthy BMI band is shown alongside them. A range from, say, 60 to 81 kg for a given height reflects reality better than any single magic number. Your actual healthy weight depends on where you feel good, how you perform, and what your doctor says, not on a 1974 formula. General reference only, not medical advice.
Who actually uses this
Clinicians and pharmacy students use Devine and the others for dosing math, which is the original job. Personal trainers occasionally reference the range when a client asks “what should I weigh?” and they want to point at something concrete. And plenty of people just plug in their height out of curiosity to see how the old formulas size them up.
If you want a single number off your current weight instead of your height, the BMI Calculator is the companion to this one.
Questions people ask
Which formula is the “right” one?
There isn’t one. Devine is the clinical default for dosing, but for a personal sense of healthy weight, the BMI range beats all four. Use the average as a rough midpoint.
Why do men and women get different numbers?
Each formula bakes in a sex-based base weight and, in some cases, a different per-inch increment, reflecting average differences in body composition. Pick the one that matches you.
My weight is above all four estimates. Is that bad?
Not necessarily. These formulas don’t see muscle. If you lift or carry more lean mass than average, sitting above them is normal and not a health flag on its own.
Does it support feet and inches?
Yep. Toggle to imperial and enter feet plus inches; the results display in pounds. Metric takes centimeters and shows kilograms.
How is the BMI range calculated?
It’s the weight that puts you at BMI 18.5 (low end) and 24.9 (high end) for your exact height, using weight = BMI x height-in-meters squared.