BMI Calculator
Enter your height and weight to instantly get your Body Mass Index (BMI) and see where you fall on the standard adult classification. Works in metric or imperial units.
← Back to all toolsWant to lose or gain weight? Get your calorie target →Enter your height and weight to see your BMI.
What is BMI?
Body Mass Index (BMI) is a screening measure calculated from your weight and height. It offers a quick estimate of whether your weight falls in a healthy range — it does not measure body fat directly, but it is a useful starting point for further assessment.
BMI = weight (kg) ÷ height (m)²BMI = 703 × weight (lb) ÷ height (in)²BMI categories for adults
For most adults aged 20 and over, the World Health Organization uses these ranges:
| BMI | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| ≥ 40.0 | Obesity class III |
Asian BMI categories (reference)
A WHO expert group recommends lower cutoffs for Asian populations: overweight at ≥ 23 and obesity at ≥ 25. You can switch the calculator to this standard.
| BMI | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5 – 22.9 | Normal weight |
| 23.0 – 24.9 | Overweight |
| 25.0 – 29.9 | Obesity class I |
| 30.0 – 34.9 | Obesity class II |
| ≥ 35.0 | Obesity class III |
Keep in mind
BMI is a screening tool, not a diagnosis. Its interpretation can be less accurate for:
- Athletes and very muscular people — muscle weighs more, so they can read a higher BMI
- Older adults — body composition changes with age
- Children and teenagers — age-based growth charts should be used instead
- Pregnancy — weight changes are not covered by the standard ranges
- Different ethnicities — the same BMI can carry different health risks
Frequently asked questions
What does BMI stand for?
BMI stands for Body Mass Index. It turns your weight and height into a single number used to estimate whether your weight is in a healthy range.
How is BMI calculated?
In metric units, divide your weight in kilograms by your height in metres squared. For example, 70 kg at 1.75 m: 70 ÷ (1.75 × 1.75) ≈ 22.9.
Is BMI accurate for everyone?
Not entirely. It does not distinguish muscle from fat, so it can be misleading for athletes, older adults, children, and pregnant people, and should be used alongside other measures.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered the normal range. Values below or above that are worth a closer look.
Does this calculator store my data?
No. All calculations happen locally in your browser. Your height and weight are never uploaded or saved.
Should I rely on BMI alone?
No. BMI is only a screening starting point. A fuller picture includes body fat, waist size, diet, and activity, and you should talk to a healthcare professional.