Different medical formulas give different results because they were derived from different populations and studies. None of them is definitively "correct" — they are all approximations. The BMI healthy weight range (18.5–24.9 kg/m²) is the most widely accepted current standard.
Devine (1974)
Widely used in pharmacology for drug dosing.
Robinson (1983)
Revision of Devine formula for clinical use.
Miller (1983)
Another revision, differs for taller individuals.
Hamwi (1964)
One of the original ideal body weight formulas.