"Ideal weight" sounds like a precise medical target, but it's actually an estimate from a formula with a surprising origin story — one developed not for fitness goals, but for calculating medication dosages accurately based on body size.
The Devine formula, published in 1974, remains the most widely used ideal weight calculation today, even though it wasn't designed as a fitness or aesthetic benchmark. Several other formulas exist too — Robinson, Miller, and Hamwi — each producing a slightly different estimate for the same height, which is a useful reminder that "ideal weight" isn't a single scientifically fixed number so much as a reasonable estimate with several valid variations.
How Ideal Weight Is Calculated
Devine formula for men: 50 kg + 2.3 kg for each inch over 5 feet
Devine formula for women: 45.5 kg + 2.3 kg for each inch over 5 feet
For someone under 5 feet tall, the formula technically produces a value below the base 50 kg or 45.5 kg figure, which is part of why it's most reliable for average adult heights rather than at the extremes.
A Worked Example
For a man who is 5'10" (10 inches over 5 feet): Ideal Weight = 50 + (2.3 × 10) = 50 + 23 = 73 kg, or about 161 lb. Using the Robinson formula instead (52 kg + 1.9 kg per inch over 5 feet) produces 52 + 19 = 71 kg (about 156 lb) — a modestly different number for the exact same height, illustrating that these are all reasonable estimates rather than one definitive answer.
Common Mistakes to Avoid
- Treating the result as a strict target: it's a population-based estimate, not a personalized clinical goal — healthy weight varies with frame size, muscle mass, and individual factors.
- Not considering the healthy BMI range instead: a full weight range (based on BMI 18.5-24.9 for your height) is often more useful than a single "ideal" number.
- Comparing across formulas without noticing they differ: Devine, Robinson, Miller, and Hamwi all produce slightly different results for the same height — pick one and use it consistently rather than mixing them.
- Forgetting the formula's original purpose: it was designed for medication dosing calculations, not as a fitness or body composition target.
Bottom Line
"Ideal weight" is a useful estimate, not a strict rule. Use an Ideal Weight Calculator to see the Devine formula's estimate for your height, and treat it as one reasonable reference point among several rather than an exact target.