Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults.

Is BMI accurate for athletes?

BMI may not be accurate for athletes or those with high muscle mass, as it doesn't distinguish between muscle and fat.

Calculator Suite

BMI Calculator

Calculate body mass index and get health category assessment

Educational use disclaimer

This calculator is for general educational purposes only and is not a medical diagnosis. Results can be incomplete or misleading for some people, including children, athletes, pregnant people, older adults, or people with medical conditions. Consult a qualified health professional for medical advice.

Body Measurements

Enter your height and weight to calculate BMI and health category

Quick Height Presets

5'0" (152cm)5'3" (160cm)5'6" (168cm)5'9" (175cm)6'0" (183cm)6'3" (191cm)

Quick Weight Presets

120 lbs (54kg)140 lbs (64kg)160 lbs (73kg)180 lbs (82kg)200 lbs (91kg)

How this calculator works

Method, formula, examples, assumptions, and review notes for this calculator.

How this calculator works

The calculator converts entered height and weight to metric units, then applies the standard adult BMI equation.
The result is mapped to adult screening categories such as underweight, healthy weight, overweight, and obesity.
Optional age and sex inputs can help frame the result, but the adult BMI equation itself does not change by sex.

Formula

Body Mass Index

BMI = \frac{weight_{kg}}{height_m^2}

Plain text formula: BMI = weight in kilograms divided by height in meters squared.

weight_kg = body weight converted to kilograms

height_m = height converted to meters

Worked examples

Adult BMI example

Inputs

Height: 170 cm
Weight: 70 kg

Calculation

Height in meters = 1.70.
BMI = 70 / 1.70^2 = 24.22.

A BMI near 24.2 falls within the standard adult healthy-weight screening range, but it does not measure body fat directly.

Curated video guide

Selected YouTube lessons that add context after the calculator, formulas, examples, assumptions, and limitations.

BMI Calculation Formula: How to Calculate Body Mass Index

Source: RegisteredNurseRN on YouTube

Why this video: Selected because it focuses on the BMI formula and unit handling as educational screening context, without treatment or weight-loss claims.

What it adds: It supplements the page's equation by walking through a manual calculation and clarifying the weight-height relationship.

Use with this calculator: Use the calculator to get the BMI quickly, then use the video to understand the arithmetic behind the displayed category.

Limits: BMI is educational screening context only and cannot assess overall health status, body composition, or an individualized care plan.

How to interpret your result

BMI is a screening measure, not a diagnosis.
People with high muscle mass, pregnancy, some medical conditions, or unusual body composition may need different assessment methods.

Assumptions

Adult BMI categories are used for adult interpretation.
Height and weight are entered accurately and measured under comparable conditions.

Limitations

BMI does not distinguish fat mass from lean mass.
BMI categories for children and teens require age- and sex-specific percentiles, not adult cutoffs.
BMI can be incomplete for athletes, older adults, pregnant people, and people with medical conditions.

Common mistakes

Treating BMI as a complete health diagnosis.
Using adult BMI categories for children or teens.
Ignoring waist circumference, body composition, medical history, and clinician assessment.

Sources

CDC: Adult BMI categories CDC: Adult BMI calculator

Disclaimer

Educational use disclaimer

Last updated and reviewed by

Updated 2026-06-06Calculator Suite editorial review