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

Is BMI accurate for athletes?

BMI can overestimate body fat in muscular people because it does not distinguish between muscle and fat. Consider body composition testing for more accuracy.

How do I interpret my BMI result?

Use the WHO categories as a guide: underweight (<18.5), healthy (18.5–24.9), overweight (25–29.9), and obesity (30+). For personalized advice consult a healthcare professional.

BMI Calculator

Calculate Your Body Mass Index (BMI)

Results

Enter your height and weight and press Calculate.

BMI Definitions & Guidance

Definitions and guidance to help users understand BMI, its uses and limitations.

What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a simple numeric measure that relates weight to height (kg/m²). It provides a quick screen for potential underweight, healthy weight, overweight, or obesity in adults. BMI is not a diagnostic of health but a useful starting point for assessing weight relative to height.

BMI formula

The metric formula is BMI = weight (kg) / (height (m))². When using imperial units: BMI = 703 × weight (lb) / (height (in))². This tool performs unit conversions and shows results to two decimal places for precision.

Categories (WHO standard for adults)

Underweight: BMI < 18.5
Normal / Healthy weight: BMI 18.5 – 24.9
Overweight: BMI 25.0 – 29.9
Obesity (Class I): BMI 30.0 – 34.9
Obesity (Class II): BMI 35.0 – 39.9
Obesity (Class III): BMI ≥ 40.0

Ideal weight range (approx.)

This calculator displays the weight range for a healthy BMI (18.5–24.9) for your height. Use it as a planning reference — individual targets can vary with age, sex, muscle mass and medical conditions.

Limitations of BMI

BMI does not separate muscle from fat. Athletes and very muscular people may have elevated BMI without excess body fat. BMI is less accurate for older adults and children; use age- and sex-specific charts or consult a clinician for precise assessment.

How to measure properly

Measure height without shoes and weight with light clothing for consistency. Use the same units each time and measure at the same time of day if tracking progress.

When to see a healthcare provider

If your BMI indicates obesity or if you have health concerns (high blood pressure, high blood sugar, abnormal lipid levels), consult a healthcare professional for a full assessment and personalized advice.