Health
How do you calculate BMI from weight and height?
Calculate your BMI from weight and height with the WHO classification.
Quick answer
BMI (body mass index) = weight in kg ÷ height in metres squared. At 70 kg and 175 cm (1.75 m): 70 ÷ (1.75 × 1.75) = 70 ÷ 3.06 = 22.9 — within the WHO normal range (18.5–24.9).
BMI
22.9
- WHO classification
- Normal weight
- Normal weight range for your height
- 56.7 – 76.3 kg
BMI is a statistical indicator and does not account for muscle mass, age or body type. It does not replace advice from a doctor or dietitian.
How it works
BMI is a quick screening tool used by doctors and insurers worldwide. It does not distinguish muscle from fat: a lean athlete and a sedentary person at the same BMI can have very different body composition. Use it as one data point, not a diagnosis.
Next steps that beat staring at a single number: measure waist at the navel (risk rises when waist is high even if BMI looks "normal"), track trends on a smart body fat scale, and pair BMI with body-fat % or the ideal-weight range for your height. A body measuring tape takes 30 seconds and catches central fat that BMI misses.
If BMI is above 25 and you are not highly muscular, calorie intake (TDEE) and weekly activity matter more than the label. If BMI is under 18.5, rule out under-fuelling before chasing a lower number for sport. General screening only — not medical advice.
There is a check that takes no formula and catches what BMI misses: keep your waist under half your height. Measure the waist at the navel and compare it with half your height in the same units — a person 175 cm tall wants a waist under about 87 cm. It works because BMI cannot see where the weight sits, and abdominal fat is the part associated with metabolic risk, while a muscular build inflates BMI without any of it. The two together are far more informative than either alone, and the waist one needs nothing but a tape measure and no arithmetic at all.
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Frequently asked questions
What BMI is considered overweight?+
WHO classification: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obesity (class I 30–34.9, II 35–39.9, III 40+). Asian populations sometimes use lower cut-offs (overweight from 23) due to different fat-distribution risk at the same BMI.
Is BMI accurate for muscular people?+
No — muscle is denser than fat, so athletes often score "overweight" on BMI despite low body fat. Waist circumference, body-fat percentage (Navy method, calipers or DEXA) or a smart scale trend give a clearer picture. If your waist is modest and strength is high, ignore the BMI label.
What is a healthy weight for my height?+
Multiply your height in metres squared by 18.5 and 24.9. At 1.75 m: 56.7–76.3 kg. The calculator shows this range automatically beside your BMI class. Aim for a zone you can hold with training and food — not the lowest number in the band.
Should children use the same BMI ranges?+
No. Paediatric BMI uses age- and sex-specific percentiles, not fixed adult cut-offs. A BMI of 20 means something different at age 8 vs age 15. This calculator is for adults (18+); for kids use a paediatric growth chart with a clinician.
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