Calculating Ideal Weight: Which Formula Is Actually Right?
Few numbers occupy people as much as their own "ideal weight". Yet even the question of how to calculate it leads into a thicket of competing formulas: Broca, Devine, the BMI healthy-weight range and body fat percentage often produce markedly different values for the same person. This guide sorts the main methods, explains where they come from and shows which approach is the most meaningful today.
First, the essential point: an "ideal weight" is an individual range, not a medical requirement. Muscle mass, build, age and general health say more than a single figure. All formulas offer only rough guidance. If you want to compare your own values directly, you can recalculate every figure in this article with your personal measurements in the <a href="/en/ideal-weight-body-fat-calculator">ideal weight and body fat calculator</a>.
The Broca Formula: Simple but Outdated
The oldest rule of thumb still in use comes from the French physician Paul Broca in the 19th century. It defines normal weight as height in centimetres minus 100. At 175 cm that gives 75 kg. The "ideal weight" lies below that: around 10 percent less for men, about 15 percent less for women. The formula's charm is its simplicity — you can do it in your head.
The big drawback: it completely ignores build and muscle share and gives unrealistic results for very tall or very short people. For a two-metre person, Broca calculates an ideal weight almost no one can reach healthily. That is why the formula is now considered obsolete and serves only as a rough comparison value.
The Devine Formula: Borrowed From Medicine
The Devine formula was developed in 1974 not as a beauty ideal but to calculate drug dosages. For men it starts from 50 kg at a height of 152 cm (five feet) and adds 2.3 kg for each additional inch; for women the base value is 45.5 kg. Because it calculates in inches and builds on a fixed reference height, it sounds more precise than it is.
In clinical practice, Devine is still used today, for example for dosing by ideal weight. As a personal weight goal, however, it is only of limited use: it too accounts for neither muscle nor individual stature and produces questionable values at the extremes of height.
The BMI Range: The Best Compromise
The key difference of the BMI method is that it gives not a single number but a range. According to the World Health Organization, a healthy normal weight corresponds to a body mass index between 18.5 and 24.9. Converting these limits back to height gives a weight range — at 175 cm, roughly 57 to 76 kg. This is exactly the range the calculator shows as the recommended value.
The range is more honest than any single figure because it acknowledges that there is no one correct weight. Its drawback: BMI does not distinguish between fat and muscle either. A well-trained person can sit above the range without being "overweight". This is where body fat percentage comes in.
Why Body Fat Often Reveals More
Two people with identical weight and identical height can look completely different and be differently healthy — depending on how much of their weight is fat and how much is muscle. Body fat percentage captures exactly this difference. The calculator estimates it with the US Navy formula from waist, neck and height and places a Deurenberg estimate alongside as a cross-check.
No circumference measurement replaces a lab test, but body fat shifts the discussion from weight alone toward body composition — and that is often more decisive for health.
Conclusion: The Range Beats the Single Figure
If you must choose one method, the BMI healthy-weight range is the best starting point: well-supported, honestly framed as a range and internationally recognised. Broca and Devine are interesting as historical rules of thumb but should never serve as a binding target. And body fat percentage rounds out the picture with the question of what the weight consists of. Compare all values in the <a href="/en/ideal-weight-body-fat-calculator">ideal weight and body fat calculator</a> — and keep in mind that a single number never decides your health.