Free adult BMI calculator

BMI Calculator

Calculate your Body Mass Index using weight in kilograms and height in centimeters. BMI is a simple screening number that compares body weight with height. It can be useful for general awareness, but it should not be treated as a diagnosis or complete health assessment.

Enter your details

This calculator uses the metric BMI formula: weight in kilograms divided by height in meters squared.

Your height and weight are processed in your browser for this calculation. No account is required.

BMI result

Enter your height and weight to see your BMI result and category.

Adult BMI categories

BMI categories are commonly used for adults as a quick screening reference. The standard adult ranges are underweight below 18.5, healthy weight from 18.5 to less than 25, overweight from 25 to less than 30, and obesity at 30 or greater.

Underweight

BMI below 18.5

Healthy Weight

BMI 18.5 to less than 25

Overweight

BMI 25 to less than 30

Obesity

BMI 30 or greater

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How BMI is calculated

BMI stands for Body Mass Index. The metric formula is:

BMI = weight (kg) ÷ height² (m²)

For example, a person who weighs 70 kg and has a height of 1.70 m would have a BMI of 70 ÷ (1.70 × 1.70), which is approximately 24.2. This gives a quick way to compare body weight with height, but it does not explain everything about a person's health.

Important limitations of BMI

BMI is useful because it is simple, but it has limitations. It does not directly measure body fat, muscle mass, bone density, waist size, fitness level, or fat distribution. Athletes and people with high muscle mass may have a higher BMI without having the same health risk as someone with a similar BMI but different body composition.

BMI may also need extra context for children, older adults, pregnant people, and some population groups. For a complete health picture, BMI is often considered alongside other information such as waist measurement, blood pressure, lab results, medical history, lifestyle, and professional assessment.

When to use this BMI calculator

Use this calculator for general personal awareness, fitness tracking, form filling, health discussions, or understanding how BMI categories work. Do not use BMI alone to make major medical, diet, or treatment decisions. If you are concerned about your weight, nutrition, or health risks, speak with a qualified healthcare professional.

Privacy note

Height and weight are personal information. This BMI calculator is designed for simple browser-based calculation and does not require a login. Avoid sharing personal health details publicly or entering them into websites unless you understand how they are used.

BMI Calculator FAQ

Is BMI a medical diagnosis?

No. BMI is a general screening number. It should not replace medical advice or a professional health assessment.

Does BMI work for athletes?

BMI can be less useful for athletes because it does not separate muscle mass from body fat.

What units does this calculator use?

This version uses kilograms for weight and centimeters for height, then converts height to meters for the BMI formula.

Can children use adult BMI categories?

Children and teens usually require age- and sex-specific growth charts, so adult BMI categories are not enough for them.