Adult BMI Calculator — Height, Weight & BMI Categories

BMI Range	Category
Below 18.5	Underweight
18.5 to less than 25	Healthy weight
25 to less than 30	Overweight
30.0 and above	Obesity

BMI Range

What the adult BMI result means

BMI divides body weight in kilograms by height in meters squared. The CDC adult categories used here apply to people aged 20 and older. This tool does not calculate age- and sex-specific percentiles for children and teens.

Worked examples

For an adult weighing 70 kg at 175 cm: convert height to 1.75 m, square it to get 3.0625, then calculate 70 ÷ 3.0625 = 22.9 when rounded to one decimal. This falls in the Healthy weight category.

For an adult weighing 180 lb at 70 in (5 ft 10 in), the result is approximately 25.8, in the Overweight category. Enter 70 inches, not 5.10.

Formula / Calculation Method

BMI = weight in kilograms ÷ (height in meters × height in meters). Pounds are converted using 1 lb = 0.45359237 kg, and inches using 1 in = 0.0254 m before applying the same formula.

How to Use This Tool

Choose the age group. Adult categories are available only for ages 20 and older.
Enter your weight and choose kilograms or pounds.
Enter height as centimeters or total inches. For 5 ft 10 in, enter 70 inches.
Calculate to see BMI rounded to one decimal and the category based on the unrounded value.

Common Use Cases

Understand how the adult BMI formula uses height and weight

Check the units and arithmetic behind a BMI result

Use BMI as one starting point for a conversation with a healthcare professional

Use the category with context

The boundaries are: below 18.5, Underweight; 18.5 to less than 25, Healthy weight; 25 to less than 30, Overweight; and 30 or above, Obesity. Classification uses the unrounded result, so a displayed value close to a boundary can look different after rounding.

BMI does not measure body fat directly or distinguish muscle from fat. It is one factor among many; it should not be used alone to decide whether to change weight. For pregnancy or an individual health assessment, discuss appropriate measures with a healthcare professional.

Children and teens need a different calculation

For ages 2–19, use the CDC child and teen calculator, which interprets BMI using age and sex. This page deliberately does not assign adult categories to that age group.

Frequently Asked Questions

Can this diagnose a health condition?

No. BMI is a screening measure, and an individual assessment needs additional information.

Why do I need to choose an age group?

The adult category thresholds used here are for ages 20 and older. Children and teens need a different interpretation.

Why are the category and rounded number close to a boundary?

The category uses the full calculation; the displayed BMI is rounded to one decimal. A value of 24.96, for example, displays as 25.0 but remains below the cutoff of 25.

BMI Calculator