BMI Calculator
Calculate your body mass index in metric or imperial units, see the WHO adult category, BMI Prime and the healthy weight range for your height.
Results
WHO adult BMI categories
| Category | BMI |
|---|---|
| Severe thinness | < 16 |
| Moderate thinness | 16 – 16.9 |
| Mild thinness | 17 – 18.4 |
| Normal weight | 18.5 – 24.9 |
| Overweight (pre-obese) | 25 – 29.9 |
| Obesity class I | 30 – 34.9 |
| Obesity class II | 35 – 39.9 |
| Obesity class III | ≥ 40 |
- BMI = weight (kg) ÷ height (m)². Categories follow the WHO adult classification. BMI Prime = BMI ÷ 25.
- For children and teens use BMI-for-age percentiles instead. BMI does not distinguish muscle from fat and is less reliable for athletes, older adults and during pregnancy.
What is BMI Calculator?
Calculates body mass index (BMI) from weight and height in kilograms and centimetres or pounds, feet and inches. It shows the WHO adult category, BMI Prime and the weight range that corresponds to a normal BMI for your height.
How to use BMI Calculator
- Choose Metric or Imperial units.
- Enter your Weight and Height.
- Read your BMI, category, BMI Prime and healthy weight range, and compare with the WHO table.
Example
70 kg, 175 cm
BMI 22.9, Normal weight, BMI Prime 0.91, healthy range 56.7 kg – 76.3 kg
When to use BMI Calculator
Use it as a quick screening measure for adults. BMI does not distinguish muscle from fat, so it misclassifies many athletes, and it is not suitable for children, teenagers (use BMI-for-age percentiles) or pregnancy. Some Asian health authorities use lower cut-offs.
How BMI Calculator works
BMI = weight (kg) ÷ height (m)². Imperial input is converted exactly (1 lb = 0.45359237 kg, 1 in = 2.54 cm). Categories follow the WHO adult classification: below 16 severe thinness, 16–16.9 moderate, 17–18.4 mild thinness, 18.5–24.9 normal, 25–29.9 overweight, 30–34.9 obesity class I, 35–39.9 class II, 40 and above class III. BMI Prime = BMI ÷ 25. The healthy range is 18.5 × h² to 24.9 × h².
Common Use Cases
- Checking your BMI category
- Finding a healthy weight range for your height
- Tracking BMI during weight loss
- Converting imperial measurements to BMI
FAQs
Is BMI accurate for athletes?
Often not. Muscle is dense, so muscular people can have an "overweight" BMI with low body fat. The Body Fat Calculator gives a complementary measure.
Can children use this calculator?
No. Children and teens need BMI-for-age percentile charts because healthy BMI changes as they grow.
What is BMI Prime?
BMI divided by 25, the upper limit of the normal range. Values above 1.0 mean above the normal range.