One Number Invented by an Insurance Company
Surprise: BMI wasn't invented by a doctor but by a Belgian astronomer in the 19th century for population studies, later adopted by US insurance companies in the 1950s to rate clients. Today it's the WHO's official standard — very useful as a first indicator, but full of surprises.
Calculate Your Number Now
The formula: weight in kg ÷ height in meters squared. A 70 kg person at 170 cm: 70 ÷ (1.7 × 1.7) = 24.2 — normal range, though near the upper limit. Get yours in seconds via the [free BMI calculator](/en/tools/bmi-calculator), including your ideal healthy weight range.
When Does the Index Deceive You?
A muscular athlete may show 'overweight' at peak health — muscle outweighs fat. Elderly people may read 'normal' despite dangerous visceral fat. The index also ignores fat distribution: belly fat is far riskier than hip fat at the same number. Hence pairing BMI with waist circumference is recommended.
Using the Metric Smartly
Treat BMI as a compass, not a verdict: it reveals trends over time (is my weight steadily rising?) and works for population comparisons. But individual health decisions need additional tests: body fat percentage, blood pressure, glucose. Your number starts the conversation with your doctor — it doesn't replace them.