Ideal Weight Calculator

Last updated: 2026-05-22

Ideal weight

Ideal weight is an estimate of a healthy body weight for a given height, derived from a formula fit to population data. There is no single correct value: the most-cited formulas disagree by roughly 5–10%, and the appropriate target for an individual depends on frame size, muscle mass, body composition, and the purpose the estimate serves. This calculator computes five of the most-cited estimates in parallel — Devine, Robinson, Miller, Hamwi, and the BMI-22 reference — so the spread between them is visible directly. The average output is a midpoint of that band, not a precise answer.

How it's calculated

Four of the formulas (Devine, Robinson, Miller, Hamwi) follow the same template: a gender-specific base weight at 5 feet (1.524 m), plus a fixed weight increment for each inch above that base. They differ only in their constants:

Devine applies the same per-inch increment to both sexes, but Robinson, Miller, and Hamwi each use a smaller increment for women — so the difference between the male and female estimates widens with height, not only at the 5-foot base.

The fifth estimate, BMI 22, is constructed differently: it returns the weight that produces a body-mass index (BMI) of exactly 22, computed from height in meters squared. The Japan Society for the Study of Obesity identifies BMI 22 as the value statistically associated with the lowest disease incidence in its population data.

Alongside the five formulas, the calculator reports the WHO healthy weight range — the weights corresponding to a BMI between 18.5 and 25. This is the range-based answer most clinicians use: rather than a single number, it gives the band within which weight is considered healthy for a given height. Each formula output above normally lands inside, or close to, this range.

Worked example

For a 170 cm man, the four classical formulas and the BMI-22 reference cluster tightly between about 64 kg and 67 kg, averaging roughly 65.5 kg. The WHO healthy-weight range (BMI 18.5–25) is far wider — about 53 kg to 72 kg.For a 5'7" man, the four classical formulas and the BMI-22 reference cluster tightly between about 141 lb and 147 lb, averaging roughly 144 lb. The WHO healthy-weight range (BMI 18.5–25) is far wider — about 118 lb to 159 lb. That a single height yields a spread rather than one number is itself the most informative output: "ideal weight" is a range, not a point.

Why there are several formulas

Each formula was derived from a different population at a different time:

• Devine (1974) was designed for medication dosing rather than health goals. Many drugs — aminoglycoside antibiotics in particular — are dosed by lean body weight, and Devine's formula was a clinical estimate of that. It remains in active hospital use.
• Robinson and Miller (1983) each reanalyzed Devine against population data and produced better-fitting alternatives. Because they fit different data, they reach slightly different answers.
• Hamwi (1964) is the oldest and was a rough guide intended for diabetic meal planning. It is rarely used for individual targets now but persists in textbooks.
• BMI 22 is empirical: it represents a statistical minimum on disease-incidence curves, and is especially well validated in East Asian populations.

Limits and edge cases

Ideal-weight formulas have known limits, and the calculator reports several estimates partly to make those limits visible:

• They ignore body composition. A 170 cm person weighing 85 kg at 12% body fat is well above every formula's estimate yet lean, while a sedentary person of the same height weighing 65 kg may be "at ideal" with 28% body fat.A 5'7" person weighing 187 lb at 12% body fat is well above every formula's estimate yet lean, while a sedentary person of the same height weighing 143 lb may be "at ideal" with 28% body fat. What makes up the weight matters more than the number on the scale; pairing this with the Body Fat % Calculator (Navy Method) gives a fuller picture.
• They were not designed as goals. Devine was for drug dosing and Hamwi for meal planning. Using either as a target weight assumes something they were never validated for.
• Accuracy degrades at height extremes. Outside roughly 152–190 cm5'0"–6'3", the four classical formulas extrapolate linearly from 5 feet and become progressively less accurate. BMI 22 scales with height squared and is the most consistent estimate for very short or very tall individuals.

Choosing a target within the band

For most adults, the average of the five estimates is a reasonable benchmark. A tighter single number can be chosen by purpose: BMI 22 is the most data-driven figure for the general population (and the best-validated for Asian populations), while the Robinson formula is the most current for clinical use. Where an individual falls within the band depends on:

• Frame size: a larger bone structure trends toward the upper end of the band, a smaller frame toward the lower.
• Muscle mass: a heavily trained person can be at or above the upper end and still be lean, because the formulas do not account for muscle.
• Age: after 60, slightly higher weights (BMI 23–25) are associated with better outcomes than the formula minimums.
• Ethnicity: South Asian and East Asian populations carry higher metabolic risk at lower BMIs, while sub-Saharan African populations often show the opposite. The classical formulas were derived primarily from European and American cohorts.

A sustainable weight monitored alongside body composition is more useful than matching a single number that was originally designed for a different purpose.