Four formulas answering the same question with slightly different math
Ideal body weight formulas exist for a specific, practical reason that predates modern body composition science: clinicians needed a fast, calculable estimate of a patient's weight for tasks like drug dosing, where dosing by actual body weight can be inappropriate for patients who are significantly overweight or underweight. Devine (1974), Hamwi (1964), Robinson (1983), and Miller (1983) all emerged from that clinical need, each proposed by a different researcher, each using a slightly different multiplier — but structurally, all four follow the same shape: start from a baseline weight at 5 feet of height, then add a fixed amount for every inch taller than that, with the per-inch factor differing by biological sex.
Because they share that same underlying structure, the four formulas tend to agree closely at average heights and diverge more as height moves further from the norm the formulas were calibrated against.
The four formulas at a glance
| Formula | Year | Known for |
|---|---|---|
| Devine | 1974 | Most widely used in clinical pharmacology and drug-dosing calculations |
| Hamwi | 1964 | The only one of the four commonly paired with a frame-size adjustment |
| Robinson | 1983 | A later refinement using a similar 5-foot-baseline structure |
| Miller | 1983 | Another 1983 refinement, close in output to Robinson at most heights |
Getting your results
Pick your biological sex.
Enter your height in centimeters.
Select your frame size: small, medium, or large.
Read the frame-adjusted Hamwi weight alongside the other three formulas' unadjusted results.
Why all four use a 5-foot baseline
Each formula's structure starts from a fixed weight value defined at exactly 5 feet (152.4 cm) of height, then adds a set amount of weight for every inch above that baseline — with the added-weight-per-inch factor set differently for men and women, reflecting average differences in frame and body composition between sexes at the time these formulas were derived. This is why the formulas were originally expressed in feet and inches, a detail worth knowing since the underlying multipliers were calibrated against that imperial baseline even though this tool accepts height in centimeters and converts internally.
What frame-size adjustment actually changes
This matters because frame size is meant to capture something the height-only baseline formula can't: two people of identical height can have genuinely different skeletal builds, and the frame adjustment is Hamwi's attempt to account for that variation without requiring an actual skeletal measurement.
Why the four results converge at average heights and spread apart elsewhere
Since all four formulas share the same 5-foot-baseline-plus-per-inch structure, their outputs cluster closely together for heights near the population averages these formulas were originally calibrated against. As height moves further from that typical range — notably tall or notably short — the small differences in each formula's per-inch multiplier compound over more inches, causing the four results to spread further apart. This is a predictable mathematical consequence of the formulas' shared structure, not a sign that any one formula is becoming more or less reliable at extreme heights specifically.
Why 'ideal weight' isn't the same question as 'healthy weight'
These formulas were built for clinical convenience — mainly medication dosing — using only height and sex as inputs, which means they structurally cannot account for muscle mass, body composition, or fat distribution. A muscular athlete and a sedentary person of identical height will get identical 'ideal weight' figures from all four formulas, despite potentially having very different body compositions and very different genuinely healthy weights for their individual bodies. For a fuller picture of healthy weight that does account for composition, BMI, body fat percentage, and other body composition markers are generally considered more informative than any single-height-based ideal-weight formula.
Common mistakes
Treating the ideal-weight figure as a personal target to hit exactly, when it's a population-based estimate that ignores individual muscle mass and body composition.
Assuming the frame-size adjustment applies to all four formulas — it's specifically a Hamwi-method feature in this tool, not a universal correction.
Expecting the four formulas to agree closely at an unusually tall or short height — divergence between them naturally grows the further height moves from the population average.
Using ideal weight interchangeably with healthy weight — they answer different questions, and body composition metrics give a fuller picture than a height-and-sex formula alone.
Real use cases
Getting a quick reference figure using the same formula-based approach clinicians historically used for medication dosing calculations.
Comparing how four established formulas differ for your specific height, rather than relying on just one.
Understanding the frame-adjusted range Hamwi's method produces for your build, from small to large frame.
Using ideal weight as one data point alongside body composition metrics for a fuller health picture.
Frequently asked questions
Q: What formulas are used?
A: Devine (1974), Hamwi (1964), Robinson (1983), and Miller (1983). All four are based on a 5-foot baseline with inches over 5 feet multiplied by a factor that depends on sex.
Q: How does the frame adjustment work?
A: Hamwi's original method suggested subtracting 10% for a small frame and adding 10% for a large frame, relative to the medium-frame value.
Q: Which formula is most accurate?
A: They all give similar results for average heights. Devine is the most widely used in clinical pharmacology. None of them account for muscle mass or body composition.
Q: Is ideal weight the same as healthy weight?
A: Not exactly. Ideal weight is a formula-based estimate; healthy weight is better assessed using BMI, body composition, and overall health markers.
Q: Are my inputs stored?
A: No — all math is local.
Q: Why do the four formulas give noticeably different results for a very tall person but nearly identical results for an average-height person?
A: Because each formula uses a slightly different per-inch weight factor applied to inches above a shared 5-foot baseline, those small per-inch differences compound over more inches at greater heights, causing the results to spread apart more the further height is from the population average the formulas were calibrated against.
Calculate your ideal weight now
Try the Ideal Weight Calculator. Want a fuller body composition picture? Check the Body Fat Calculator and Lean Body Mass Calculator. Planning nutrition around your results? See the Calorie Calculator.
