Everyday & industry
BMI Calculator
Calculate Body Mass Index from height and weight and see the standard adult BMI classification. For adults age 20 and older.
Enter your height and weight to calculate Body Mass Index (BMI) and see the standard adult BMI classification associated with the result.
BMI is a broad screening measure and does not account for factors such as muscle mass, body composition, age, sex, ethnicity, or individual health circumstances.
For adults age 20 and older.
Choose a calculation mode and unit system. Metric uses centimetres and kilograms; imperial uses feet, additional inches and pounds. Each unit system retains its own entered values; switching units does not convert the inputs. Weight Comparison uses the same height for both weights. BMI Target Range Reference calculates a mathematical weight for your entered reference BMI.
Calculations run locally in your browser. Your inputs are not saved.
Enter height and weight measurements.
Example BMI Calculation
Static example: height 175 cm (1.75 m), weight 75 kg. BMI = 75 ÷ 1.75² = 24.4898…, displayed as 24.5. Standard adult BMI classification: Healthy weight. The BMI 18.5–24.9 weight reference is 18.5 × 1.75² = 56.65625 kg to 24.9 × 1.75² = 76.25625 kg, displayed approximately as 56.7 kg – 76.3 kg. This range reflects BMI mathematics only and is not a personalized weight recommendation.
About this calculator
Understanding the BMI reference
BMI is weight relative to squared height. Standard adult categories are broad screening references, not diagnoses or descriptions of personal health or fitness.
- Metric: BMI = weight in kilograms ÷ (height in centimetres ÷ 100)².
- Imperial: total height in inches = feet × 12 + additional inches. BMI = 703 × weight in pounds ÷ total height in inches².
- The classification uses the full calculated value before display rounding: below 18.5 is Underweight; 18.5 to below 25 is Healthy weight; 25 to below 30 is Overweight; 30 or above is Obesity.
- Weight corresponding to BMI 18.5–24.9 at this height is a mathematical reference, not an ideal weight or personalized weight recommendation.
- The upper weight reference uses BMI 24.9 exactly; the classification itself includes all unrounded values below 25.
Imperial BMI example
Static example: 5 ft 9 in is 69 inches. At 165 lb, BMI = 703 × 165 ÷ 69² = approximately 24.36, displayed as 24.4. The standard adult BMI classification is Healthy weight.
Frequently asked questions
What is BMI?
Body Mass Index is a numerical screening measure calculated from weight and height. It does not directly measure overall health or fitness.
How is BMI calculated?
Metric BMI is weight in kilograms divided by height in metres squared. Imperial BMI is 703 times weight in pounds divided by total height in inches squared.
What are the standard adult BMI categories?
Below 18.5: Underweight. 18.5 to below 25: Healthy weight. 25 to below 30: Overweight. 30 or above: Obesity. These are standard adult BMI classifications, not diagnoses.
Does BMI measure body fat?
No. BMI does not directly measure body fat, muscle mass or body composition.
Why can BMI be misleading for some people?
BMI does not distinguish muscle from fat or account for factors such as body composition, age, sex, ethnicity or individual health circumstances. The same BMI can have different contexts for different people.
Is BMI used differently for children?
BMI for children and adolescents is interpreted using age- and sex-specific percentile methods, which this adult calculator does not provide.
This tool provides general informational estimates and is not medical advice. BMI is a screening measure and does not directly measure body fat, fitness, or overall health. Discuss health concerns with a qualified healthcare professional.