About this tool
The body mass index (BMI) relates body weight to height: weight in kilograms divided by the square of height in meters. At 70 kg and 1.75 m that is 70 ÷ 1.75² ≈ 22.9. The World Health Organization (WHO) uses this value to classify adults from underweight through normal weight to three classes of obesity.
This calculator shows your BMI, the WHO category and the weight range that corresponds to a BMI of 18.5 to 24.9 at your height. You can use metric units (kg, cm) or pounds, feet and inches. Your entries stay in your browser.
The BMI is a simple guide, not a diagnosis: it does not account for muscle mass, build, age or sex. For a health assessment, talk to your doctor.
How it works
- Choose the units: metric or imperial.
- Enter your weight and height.
- Read your BMI and WHO category – the bar shows where you are.
- Below the result you see the normal weight range for your height.
Frequently asked questions
What BMI is normal?
According to the WHO, a BMI from 18.5 to below 25 counts as normal weight for adults. Lower values count as underweight, 25 to below 30 as overweight (pre-obese) and 30 or more as obesity.
Does the BMI apply to children and teenagers?
Not with these thresholds. Children’s and teenagers’ bodies are still changing a lot, so age- and sex-specific percentile charts are used. This calculator is meant for adults aged 18 and over.
Why can my BMI be high although I am fit?
Muscle is heavier than fat. Athletic people with a lot of muscle mass can therefore have a higher BMI despite a low body fat percentage. Conversely, a normal BMI can hide a high fat percentage. Waist circumference or body fat measurement are often used in addition.
Do the thresholds change with age?
The WHO classification applies to all adults equally. Some medical societies consider slightly higher values harmless for older people. Have this assessed individually by a doctor.
How do I convert pounds and feet to kilograms and centimeters?
One pound is about 0.4536 kg, one foot 30.48 cm and one inch 2.54 cm. The calculator does this automatically. For other units, use the Unit Converter.