BMI Calculator
Body Mass Index (BMI) is a measure that relates weight and height to assess whether a person has a healthy weight. It is calculated by dividing weight in kilograms by height in meters squared (BMI = kg / m²). According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 indicates normal weight. For example, a person weighing 70 kg and 1.75 m tall has a BMI of 22.9 (normal weight). This calculator supports both metric (kg/cm) and imperial (lbs/in) systems and shows your category with the healthy weight range for your height.
Frequently Asked Questions
What is BMI and how is it calculated?
BMI (Body Mass Index) is a measure that evaluates the relationship between weight and height. It is calculated by dividing weight in kilograms by height in meters squared: BMI = weight (kg) / height² (m). It is the most widely used tool worldwide to classify body weight according to the World Health Organization (WHO) categories.
What are the BMI categories according to the WHO?
The WHO classifies BMI as: Underweight (less than 18.5), Normal weight (18.5 to 24.9), Overweight (25 to 29.9), Obesity class I (30 to 34.9), Obesity class II (35 to 39.9), and Obesity class III (40 or more). These categories apply to adults over 18 years old.
Is BMI accurate for everyone?
BMI is a useful indicator at the population level, but it has individual limitations. It does not distinguish between muscle mass and fat, so athletes with a lot of muscle may have a high BMI without excess fat. It also does not consider body fat distribution, age, or sex. For a complete assessment, consult a healthcare professional.
What is the ideal weight for my height?
The healthy weight range is calculated using the normal BMI limits (18.5 to 24.9) multiplied by your height in meters squared. For example, for a person 1.70 m (5'7") tall, the healthy range is 53.5 kg to 71.9 kg (118 to 158 lbs). Our calculator automatically shows this personalized range.
How do you convert between metric and imperial systems?
To convert: 1 kilogram = 2.205 pounds, 1 inch = 2.54 centimeters. If using the imperial system, the BMI formula is: BMI = (weight in pounds × 703) / (height in inches)². Our calculator does the conversion automatically — just select your preferred unit system.