Calculator · Performance Lab
BMI Calculator
Body-Mass-Index by WHO standard. A quick orientation — with an honest read on its limits.
Ergebnis
- BMI
- 24.7kg/m²
- WHO category
- Normal weight
Ratio of weight to height squared.
World Health Organization classification.
Important: BMI does not distinguish between muscle and fat mass. Trained, muscular people are often misclassified as overweight. For athletes, body-fat percentage and FFMI are far more meaningful.
Explained
What this calculator does for you
Body-Mass-Index relates your weight to your height squared. It gives a quick, coarse classification — no more, but no less.
Crucially: BMI does not distinguish a kilo of muscle from a kilo of fat. Anyone training seriously often lands in 'overweight' or even 'obese class I' while their body-fat sits in the athletic range.
Use BMI as a rough compass. For an honest read on body composition, body-fat percentage and FFMI are the better numbers.
Science
Scientific background
BMI was developed in the 19th century by Belgian statistician Adolphe Quetelet — as a population-level statistical measure, not an individual diagnosis.
The WHO uses it today as a screening tool: above BMI ≥ 30, statistical risks for cardiovascular disease, type-2 diabetes and other conditions rise measurably.
Its limits are well documented: athletes, very tall or very short people, the elderly and pregnant women fall outside its meaningful range.
Examples
Practical examples
Example A — 180 cm, 80 kg
BMI ≈ 24.7 → normal weight. Typical for a moderately trained person.
Example B — 180 cm, 95 kg, very muscular
BMI ≈ 29.3 → 'overweight' on the table. A body-fat reading of ~12 % shows the cause is muscle, not fat.
Avoid these
Common mistakes
- 01Treating BMI as an individual diagnosis. It is a population screen — not your body image.
- 02Labelling muscular people as 'overweight'. Use body-fat measurement instead.
- 03Ignoring very low BMIs. Underweight is medically relevant.
- 04Applying BMI uncritically to pregnant women, the elderly or children.
Recommendations
Further recommendations
- 01Always combine BMI with body-fat percentage and waist circumference.
- 02For athletes, FFMI is far more informative — it corrects for height and focuses on fat-free mass.
- 03Serious trainees should orient themselves by the mirror, performance and body-fat — not a height/weight table.
FAQ
Frequently asked questions
- I train seriously and my BMI says overweight — am I too heavy?
- Very likely no. Muscle is denser than fat. Measure your body-fat percentage (e.g. with our circumference method) and check the mirror — both are more honest than BMI.
- Which categories apply?
- WHO standard: below 18.5 underweight; 18.5–24.9 normal; 25.0–29.9 overweight; 30.0–34.9 obese class I; 35.0–39.9 obese class II; ≥ 40.0 obese class III.
- Are there complementary measures?
- Yes: body-fat percentage, waist-to-hip ratio and waist circumference. They say more about real metabolic risk than BMI alone.
- Is a low BMI always good?
- No. Very low BMI can indicate undernutrition, illness or muscle wasting. Underweight is clinically relevant too.
- Does BMI work the same for children or the elderly?
- No. Children and adolescents use age- and sex-specific percentiles. For the elderly the 'healthy' corridor shifts slightly upward.
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