BMI Calculator
Enter your weight and height to get your Body Mass Index and see which WHO weight category it falls into.
How it works
BMI is calculated by dividing your weight in kilograms by the square of your height in metres. The result is compared against WHO's standard bands to classify it as underweight, normal weight, overweight, or obese. BMI is a population-level screening tool, not an individual diagnostic measure.
Formula
BMI = weight (kg) ÷ height (m)²
Body Mass Index divides your weight by the square of your height, giving a single number used to broadly classify body-weight categories.
| Symbol | Variable | Unit | Description |
|---|---|---|---|
| weight | Body weight | kg | |
| height | Height | m |
Worked example
70kg, 1.75m
- Weight:
- 70 kg
- Height:
- 1.75 m
BMI = 70 ÷ 1.75² = 70 ÷ 3.0625 ≈ 22.9, which falls in the Normal weight range.
Limitations
Doesn't account for muscle mass, bone density, fat distribution, age, sex, or ethnicity, and isn't validated for children, pregnant people, or the very elderly.
Frequently asked questions
Is BMI accurate for athletes?
Not always. BMI doesn't distinguish muscle from fat, so muscular athletes can show a high BMI despite low body fat. Body fat percentage is a better measure in that case.
What's a healthy BMI range?
The WHO classifies 18.5–24.9 as normal weight for most adults. Ranges can vary somewhat by population and are less reliable outside typical adult body types.
Does BMI account for age or sex?
No, this calculator uses the standard adult bands, which don't adjust for age or sex. Children and teenagers require different, age-specific BMI-for-age charts.
Should I make health decisions based on BMI alone?
No. BMI is a quick screening estimate. Combine it with other measures (waist circumference, body composition) and a healthcare professional's assessment before drawing conclusions.
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Last reviewed: 2026-08-22.