The Ideal Body Weight Calculator and the Historical Hamwi Weight Formula Calculator both produce height-based weight estimates descended from the same family of historical “ideal body weight” equations, and both pages are careful to label them as heuristics rather than health targets. The ideal body weight calculator applies the 1974 Devine formula and pairs it with the BMI 18.5–24.9 healthy weight band for the same height. The healthy-weight page reproduces the Hamwi equation with small, medium, and large frame multipliers as a range. One reports a single point beside a screening range; the other reports a frame-adjusted range from a retained historical formula.
What each calculator does
The Ideal Body Weight Calculator takes sex and height, in centimeters or feet and inches, and applies the Devine formula: men get 50 kg at 5 feet plus 2.3 kg per inch over, women 45.5 kg plus 2.3 kg per inch over. The result rounds to one decimal place — a 180 cm man gets 75.0 kg. Two supporting readouts follow: the healthy weight band for that exact height (for 1.80 m, 59.9–80.7 kg) and the 18.5–24.9 band itself. The page frames the Devine number as a 1974 gentamicin-dosing heuristic, not a weight-loss target, and points to the BMI-based band as the population screening reference.
The Historical Hamwi Weight Formula Calculator takes a height unit (centimeters or feet-and-inches), a result unit, the male or female equation, and a small, medium, or large frame assumption. The Hamwi base is 48 kg plus 2.7 kg per inch over 152.4 cm for men, and 45.5 kg plus 2.2 kg per inch over for women. The frame assumption then multiplies the base into a range: 0.90–0.95 for small, 0.95–1.05 for medium, and 1.05–1.10 for large. The default of 170 cm, male, medium frame gives a base of about 66.7 kg and a range of 63.4–70.0 kg. In feet mode, the digits after the decimal are inches — 5.7 means 5 feet 7 inches, not 5.7 feet. The page labels the result a retained historical assumption without support from authoritative sources, not a healthy body weight.
Side-by-side
| Ideal Body Weight (Devine) | Historical Hamwi Weight Formula | |
|---|---|---|
| Formula basis | Devine 1974: 50/45.5 kg base + 2.3 kg per inch over 5 ft | Hamwi: 48/45.5 kg base + 2.7/2.2 kg per inch over 152.4 cm |
| Inputs | Sex, height in cm or feet and inches | Height unit, result unit, sex equation, frame assumption |
| Output | One Devine number plus the BMI healthy band | Base weight plus a frame-adjusted range |
| Frame size | Not modeled | Small/medium/large multipliers (0.90–1.10) |
| Health framing | Dosing heuristic; BMI band shown as screening reference | Explicitly historical; not a health verdict |
| 170 cm man | About 65.9 kg (Devine point) | Base about 66.7 kg; medium frame 63.4–70.0 kg |
When to use which
Use the Ideal Body Weight Calculator when you want the Devine number presented honestly next to the BMI-based healthy band for the same height — its stated purpose is pairing the legacy heuristic with a population screening range. It is also the page to use when you want the healthy weight range defined by CDC adult BMI categories.
Use the Historical Hamwi Weight Formula Calculator when you want to reproduce the Hamwi equation itself, including the small/medium/large frame multipliers, or when you are comparing equation conventions from the historical ideal-body-weight family. It is the only one of the two that models frame size.
Neither tool should drive a weight-loss target or a clinical decision. For clinical dosing, the ideal body weight page advises confirming with a pharmacist or clinician which weight convention (actual, ideal, adjusted, or lean) a specific medication protocol requires — it varies by drug.
Limits and disclaimer
Both formulas derive from mid-century height-weight tables, not from research on what weight is healthiest — as documented in the Pai and Paloucek review of the origin of the ideal body weight equations — and they were adopted for dosing calculations for which they were not originally designed. Neither calculator accounts for muscle mass, age, or medical context, and the Hamwi frame multipliers are retained historical assumptions rather than measurements. The healthy band on the ideal body weight page is a BMI 18.5–24.9 population screening range with the caveats that apply to BMI itself, not a personal prescription. Both pages are educational only and are not medical advice.