"Ideal body weight" sounds like a single, precise number. In practice, it depends entirely on which 20th-century formula you ask.
Devine formula ideal body weight, the most commonly cited
For a 180 cm man, the Devine formula (1974, originally built for drug-dosing calculations) gives 75.0 kg. It's the most frequently referenced of the four classic formulas.
Hamwi formula calculator, and the other three
Run the same height through Robinson (1983): 72.6 kg. Miller (1983): 71.5 kg. Hamwi (1964): 77.3 kg. That's a 5.8 kg spread across four formulas for the identical height — averaging to 74.1 kg, but no single formula is "the" correct answer.
Ideal body weight by height, why this calculator shows all four
Most calculators pick one formula and present it as definitive. Showing all four side by side, plus their average, makes the real uncertainty visible instead of hiding it behind a single confident-looking number — these formulas were built for medical dosing purposes decades ago, not as personal health targets.
