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Calculation of ideal weight
Three historical formulas for estimating a reference weight. Use as a benchmark, not a sole objective.
Why several formulas?
No formula is universally valid. They were developed at different times (1960-1980) for different populations, with different objectives (public health, medicines, military recruitment). Comparing several results gives a fairer range than a single number.
The three formulas used
Lorentz (1929)
Separate men and women. Simplest formula: (size − 100) − (size − 150) / coef. Often perceived as a little low for women.
Creff (1981)
Incorporates age (“ideal” weight increases with age) and body shape. Suitable for clinical reading, but subjective on the definition of "morphology".
Guess (1974)
Originally designed for drug dosing. Widely used in medicine to calculate doses. Often underestimate the ideal weight of very tall people.
Important limitations
These formulas only take into account size (and, for Creff, age and body shape). They ignore body composition: a muscular athlete can weigh significantly more than his "ideal weight" without any health problems.
For a more detailed reading: combine with the BMI (which places it in a healthy range) and the fat mass rate (which distinguishes between muscle and fat). The “ideal weight” remains a theoretical benchmark, never a strict objective.
Questions fréquentes
None. They all give an estimate, with ±5 kg of difference between them. The average of the three is a reasonable compromise, but must be supplemented by BMI and body fat percentage.
Creff considers that a slightly higher weight after the age of 40 is associated with better resistance to disease (clinical study from the 1980s). This idea remains debated in recent literature.
Not really. A rugby player or weightlifter can exceed their “ideal weight” by 15-20 kg with a very low body fat. For athletes, body fat is a much better indicator.