For adults, a BMI between 18.5 and 24.9 is generally considered normal. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obesity. BMI is a screening tool and does not account for muscle mass or body composition.

How is BMI calculated?

BMI = weight (kg) ÷ height (m)². You can use metric (kg, cm) or imperial (lbs, feet and inches); this calculator converts to metric and gives your BMI and category.

Is BMI accurate for athletes?

BMI does not distinguish muscle from fat. Athletes with high muscle mass may have a high BMI despite low body fat. For body composition, use our body fat calculator or body fat analyzer.

What is the BMI range for obesity?

A BMI of 30 or above is classified as obesity (Class 1: 30–34.9, Class 2: 35–39.9, Class 3: 40+). BMI is a screening tool; discuss your health goals with a doctor.

BMI Calculator

Body Mass Index (BMI) is a number based on your weight and height. It is used as a simple screening tool to place adults into broad categories (underweight, normal weight, overweight, obesity). BMI does not measure body fat directly and does not account for muscle mass, age, or sex.

What Is the BMI Calculator?

The BMI calculator computes your Body Mass Index from your weight and height. BMI is a simple screening number used to place adults into broad categories: underweight, normal weight, overweight, and obesity. It does not measure body fat directly but is widely used in health and research as a quick weight-for-height indicator.

How Does the BMI Calculator Work?

The formula is BMI = weight (kg) ÷ height (m)². You enter your weight and height in metric (kg, cm) or imperial (lbs, feet and inches); the calculator converts to metric and gives your BMI plus the category (e.g. normal, overweight). No age or sex is used in the standard BMI formula.

Why Use This BMI Calculator?

A BMI calculator gives you a fast way to see where you sit on the standard weight-for-height scale. It is useful for general awareness and for comparing with health guidelines. For a better picture of body composition, pair it with our body fat calculator or ideal body weight calculator. For calorie and weight goals, use our calorie calculator.

Who Should Use This Tool?

Adults who want a quick weight-for-height check can use this BMI calculator. It is intended for general screening, not as a sole measure of health. Athletes and very muscular people may have a high BMI despite low body fat; older adults or those with low muscle mass may have a "normal" BMI but carry more fat. Use BMI as one reference alongside other tools and professional advice.

Is This Calculation Accurate?

The BMI formula is accurate as a math result; the number itself is correct for your weight and height. What varies is how well BMI reflects health or body fat for each person. It does not account for muscle mass, bone density, age, or sex. For body composition, consider our body fat calculator; for daily nutrition, use the TDEE calculator.

Frequently Asked Questions

What is a good BMI?
For adults, a BMI between 18.5 and 24.9 is generally considered normal. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obesity. BMI is a screening tool and does not account for muscle mass or body composition.
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². You can use metric (kg, cm) or imperial (lbs, feet and inches); this calculator converts to metric and gives your BMI and category.
Is BMI accurate for athletes?
BMI does not distinguish muscle from fat. Athletes with high muscle mass may have a high BMI despite low body fat. For body composition, use our body fat calculator or body fat analyzer.
What is the BMI range for obesity?
A BMI of 30 or above is classified as obesity (Class 1: 30–34.9, Class 2: 35–39.9, Class 3: 40+). BMI is a screening tool; discuss your health goals with a doctor.

Related Tools

After checking your BMI, explore the ideal body weight calculator for a height-based weight range, the body fat calculator for composition, and the calorie calculator for daily intake goals. More in our blog.