Ideal Body Weight Calculator
Ideal body weight
– kg
Enter a height and pick a sex.
- Adjusted body weight
- –
- Formula
- –
All four formulas
| Formula | Ideal body weight |
|---|
This works out the arithmetic. The order, the product in your hand and local policy still govern what is given.
The Devine formula
Male: 50 kg + 2.3 kg per inch over 5 ft · Female: 45.5 kg + 2.3 kg per inch over 5 ft
Every formula here works the same way: a base weight at five feet, plus a fixed amount for each inch above that. They differ in both numbers, which is why a 178 cm man comes out anywhere between 70.4 kg and 75.2 kg depending on which is used.
Devine published this in 1974 to standardise gentamicin dosing. It was never intended as a statement about healthy body weight, and reading it that way is a misuse of it that has outlived the original paper by fifty years.
Adjusted body weight and when it is used
Adjusted body weight = ideal + 0.4 × (actual − ideal)
Some drugs distribute into fat and some do not, so for a patient well above their ideal weight neither figure is right. Adjusted body weight splits the difference at 40%, which is the factor in general use.
A man of 178 cm weighing 120 kg has an ideal weight of 73.2 kg by Devine and an adjusted weight of 91.9 kg. The gap between those and his actual weight is exactly the spread that makes the weight choice in thecreatinine clearance calculator matter.
Questions about ideal body weight
- What is the Devine formula for ideal body weight?
- For a man, 50 kg plus 2.3 kg for every inch of height over five feet. For a woman, 45.5 kg plus 2.3 kg per inch over five feet. It was published in 1974 in the context of gentamicin dosing, not as a description of a healthy weight.
- What is adjusted body weight used for?
- Some drugs distribute partly into adipose tissue, so neither actual nor ideal weight fits. Adjusted body weight is ideal weight plus 40% of the difference between actual and ideal, and it is used where a dosing reference specifically calls for it.
- Is ideal body weight a healthy weight?
- No. These formulas were derived for drug dosing and give a single number from height and sex alone, ignoring build, muscle mass and body composition. They are not a target weight and should not be read as one.
- What if someone is shorter than five feet?
- Every formula here is built on inches above five feet, so below that height they are being extrapolated rather than applied. Paediatric and short-stature dosing generally uses actual weight or a different method entirely.