"Ideal weight" calculators almost always use the Devine formula, published in 1974 — but it's worth knowing where this number actually comes from before treating it as a target.
Where the Devine formula comes from
The Devine formula was originally created to help clinicians estimate a patient's weight for medication dosing calculations, not as a public health recommendation. It's a linear formula based on height alone: 50 kg (men) or 45.5 kg (women) as a base, plus 2.3 kg for each inch over 5 feet tall.
Worked examples
A 180 cm (about 5'11") man: Devine ideal weight ≈ 75 kg. A 165 cm (about 5'5") woman: Devine ideal weight ≈ 56.9 kg.
A healthy weight is really a range, not one number
Because BMI's healthy range (18.5–24.9) spans a wide band, a more useful reference is often the weight range that keeps someone in that band at their height, not a single "ideal" figure. For the 180 cm example above, that healthy-BMI range works out to roughly 59.9–80.7 kg; for 165 cm, roughly 50.4–67.8 kg.
What this formula doesn't account for
- Body composition: like BMI, it doesn't distinguish muscle from fat, so it can understate a healthy weight for muscular individuals.
- It's not an official public health guideline: unlike BMI categories (which the WHO defines) or dietary intake recommendations, there's no equivalent government body that has adopted the Devine formula as a health target — it remains a clinical dosing convention.
Common mistakes
- Treating the single Devine number as a strict target rather than a rough reference point — the healthy-BMI weight range is usually more informative.
- Assuming this formula reflects official health guidance the way BMI categories do.
Get your own estimate and healthy weight range with the Ideal Weight Calculator.