What "Ideal Weight" Actually Means
"Ideal body weight" (IBW) formulas were created for medicine, not vanity — originally to standardize drug dosing and clinical assessment by height and sex. Each produces a single reference point, and because they were derived differently, they disagree slightly. That disagreement is the honest answer: your ideal is a range, not a number.
This calculator shows four classic formulas side by side plus the BMI-derived healthy band (18.5–24.9), giving you a defensible target zone rather than a false-precision bullseye.
The Four Formulas
All four use the same structure — a base weight at 5 feet, plus an increment per inch over:
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 kg + 2.3/inch | 45.5 kg + 2.3/inch |
| Robinson (1983) | 52 kg + 1.9/inch | 49 kg + 1.7/inch |
| Miller (1983) | 56.2 kg + 1.41/inch | 53.1 kg + 1.36/inch |
| Hamwi (1964) | 48 kg + 2.7/inch | 45.5 kg + 2.2/inch |
Worked example — woman, 5'6" (167.6 cm)
| Devine | 45.5 + 2.3×6 = 59.3 kg |
| Robinson | 49 + 1.7×6 = 59.2 kg |
| Miller | 53.1 + 1.36×6 = 61.3 kg |
| Hamwi | 45.5 + 2.2×6 = 58.7 kg |
| BMI 18.5–24.9 band | 52.0 – 69.9 kg |
The formulas cluster around 59–61 kg; the BMI band brackets them generously. Anywhere inside that band with good habits is a legitimate "ideal."
Why the Formulas Can't Know You
Height and sex are all these equations see. They're blind to:
- Muscle mass — a trained 5'10" man at 85 kg can be leaner than an untrained one at 75 kg. Composition beats scale weight; check the Body Fat Calculator.
- Frame size — wrist/elbow breadth shifts healthy weight by ±5% or so in older clinical practice.
- Age — modestly higher weights in seniors correlate with better outcomes in several studies.
- Fat distribution — waist size predicts metabolic risk better than total weight; the BMI Calculator pairs both.
Use IBW as a navigation aid: if you're far outside the band, direction is clear; once inside it, composition, fitness, labs, and how you feel are the better instruments.
Setting a Real Target From the Range
- Pick the band, not a point: the formula cluster ±3–4 kg is a rational first target zone.
- Adjust for training history: muscular builds should target the upper half (or use body-fat % instead).
- Plan the pace: 0.25–0.5 kg/week via a moderate calorie adjustment — the Calorie Calculator converts your target into daily calories.
- Re-anchor on progress markers — waist, energy, strength, labs — not just the scale.
The Bottom Line
Four medical formulas and the BMI band give you an honest target zone in seconds — and the spread between them is a built-in reminder that biology doesn't do single perfect numbers. Land in the band, build muscle, watch the waist, and let health markers — not a formula from 1974 — make the final call.