SBMI (Smart Body Mass Index) is an extended version of BMI, proposed in the smartbmi.com project. Ordinary BMI does not account for age and sex, so the same value in a young man and an older woman is interpreted the same way — which is not always correct. SBMI tries to fix this.
The result is expressed not in kg/m² but as points on a scale from 0 to 70, where the position on the scale reflects weight-related health risk adjusted for age and sex. It is a way to interpret weight more gently and precisely than "raw" BMI or BMI Prime.
Reference ranges
SBMI is not a physical quantity but a points-based risk estimate. Guides along the scale:
| Scale range | 0 – 70 points |
| Central (optimal) zone | low health risk |
| Shift down the scale | underweight |
| Shift up the scale | overweight / obesity |
What an elevated level means
High SBMI scores (the upper part of the scale) mean overweight or obesity adjusted for age and sex — a reason to assess body fat percentage, the waist and metabolism, not weight alone.
What a low level means
Low scores (the lower part of the scale) indicate underweight. In older people, too low a weight is no less dangerous than excess, because of the loss of muscle and bone mass.
How the test is done
SBMI is calculated by an online calculator from four parameters: height, weight, age and sex. It is based on the same BMI (weight / height²), but the result is normalized for age and sex and converted to a point on the 0–70 scale. There is no separate "at-home" formula.
What affects the value
- Incorrectly entered age or sex shifts the estimate — they are key.
- High muscle mass: like BMI, SBMI can overstate risk in athletes.
- Edema, dehydration distort weight and therefore the score.
Calculate using this marker
Calculators where Smart BMI (SBMI) is used directly:
Frequently asked questions
How does SBMI differ from ordinary BMI?
SBMI additionally accounts for age and sex and gives a score on a 0–70 scale rather than a value in kg/m². This makes the interpretation of weight more individual, but it is based on the same BMI.
What SBMI is considered good?
The central part of the scale is optimal — it corresponds to the lowest weight-related risk for your age and sex. The exact zone boundaries are set by the calculator; interpret the result together with your waist and body composition.