BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight, and see your WHO weight category.
Formula last reviewed 4 August 2026 · How we verify our calculators
Your BMI
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Frequently asked questions
BMI is your weight in kilograms divided by your height in metres squared (kg/m²). For 70 kg at 1.75 m, BMI ≈ 22.9.
The WHO ranges are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obese.
Not always. BMI does not distinguish muscle from fat, so very muscular people can read as “overweight” despite low body fat. Pair it with a body-fat estimate for context.
Some health bodies use lower thresholds for Asian adults because risk rises at a lower BMI. Treat the standard categories as a general guide and consult a professional.
Same weight, 10cm shorter, a different WHO category entirely
70 kg at 175 cm works out to a BMI of 22.9 — squaring the height in metres (1.75² = 3.0625) and dividing weight by that — which lands squarely in the WHO Normal range (18.5–24.9). Keep the exact same weight but drop the height to 165 cm, and the BMI climbs to roughly 25.7, crossing into Overweight. Nothing about the person's actual body changed except the denominator — which is the entire point of BMI: it's a ratio, never a standalone weight figure.
Why this simple ratio became the global standard
Weight (kg) ÷ height (m)² is the whole formula, and its popularity comes precisely from that simplicity — no equipment beyond a scale and a tape measure, no lab, no specialist required, which is why it remains the default screening tool doctors and health bodies reach for first. Enter your numbers and you're placed instantly into one of four WHO bands: underweight, normal, overweight or obese.
What a single ratio can't see
BMI's real limitation is structural, not a matter of precision: because it only ever sees height and weight, it has no way to distinguish muscle from fat. A heavily muscled athlete can score "overweight" or worse despite carrying very little actual body fat, and two people with an identical BMI can carry their weight in completely different places on the body — a distinction that matters for health risk but is invisible to this formula. That's why BMI works best as a quick screening signal rather than a diagnosis: pair it with the body-fat calculator for actual composition, and the ideal-weight calculator for a height-based reference point, before drawing any real conclusions from the number alone.
This is a general estimate, not medical advice. Consult a doctor or registered dietitian for personalised guidance.
Sources
- World Health Organization — BMI classification for adults