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BMI calculator

Calculate your Body Mass Index (BMI) and see the WHO classification.

lb
ft
in
Your BMI
22.7
ClassificationNormal weight
Healthy weight range125.3–168.6 lb

BMI is a general reference and does not separate lean mass from fat. Consult a health professional.

Guide BMI: what it is and how to calculate Interactive lesson: What BMI can't see The same BMI can describe an athlete or someone out of shape. See what the index measures — and what it misses.

How the calculation works

Body Mass Index (BMI) relates weight and height:

BMI = weight (kg) ÷ height² (m)

Classification table (WHO)

BMICategory
under 18.5Underweight
18.5 – 24.9Normal weight
25.0 – 29.9Overweight
30.0 – 34.9Obesity class I
35.0 – 39.9Obesity class II
40+Obesity class III

What BMI can't see

BMI doesn't separate muscle from fat, nor say where fat sits. A muscular athlete can be BMI 27 with little fat; a sedentary person can be BMI 23 with high abdominal fat. Pair it with the waist-to-height ratio (waist < half your height) and, if possible, body-fat percentage.

If your BMI came out high

It's not a diagnosis — it's a signal to look further. Practical next steps: measure your waist, talk to a health professional, and if appropriate use our calorie-deficit calculator for a gradual plan.

Examples

  • A person 1.75 m tall weighing 70 kg: 70 ÷ (1.75 × 1.75) = BMI 22.9 — inside the range considered normal (18.5 to 24.9). At that height, the healthy range runs from 56.7 kg to 76.3 kg.
  • A person 1.68 m tall weighing 92 kg: 92 ÷ (1.68 × 1.68) = BMI 32.6 — class I obesity. Reaching 24.9 would mean getting down to about 70.3 kg.

Frequently asked questions

Does BMI apply to athletes?

Not always: very muscular people may have a high BMI without excess fat. Other measures fit better in those cases.

What is the ideal BMI?

For adults, the WHO healthy range is 18.5–24.9, regardless of sex. In older adults, slightly higher values can be acceptable — individual assessment matters more.

Is BMI the same for men and women?

The formula and ranges are the same. Interpretation differs: women tend to carry more fat at the same BMI, men more lean mass.

Does it work for children?

Not with these ranges. Children and teens use age- and sex-specific percentile curves — ask a pediatrician.

Can an athlete have an obese BMI?

Yes, and it happens often. BMI cannot tell muscle from fat: two men at 1.80 m and 93 kg share a BMI of 28.7 — one may be a rugby player at 12% body fat and the other sedentary at 32%.

What is the ideal weight for my height?

There is no single ideal weight, only a range. Multiply height squared by 18.5 and by 24.9. For 1.70 m that is 53.5 kg to 72.0 kg.

Does BMI apply to children and pregnant people?

Not in the same way. Children and teens use age- and sex-specific percentile charts, and pregnancy has its own weight-gain guidance based on pre-pregnancy BMI.

What is the waist-to-height ratio?

Waist circumference divided by height in the same units. The common guideline is to keep it under 0.5 — waist below half your height. It captures abdominal fat, which BMI misses.

Sources and references

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Updated on June 17, 2026 · by Rafael Rossi · Methodology & sources