BMI Calculator

By the FastFreeTools Editorial Team · Last reviewed: May 2026 · See our Editorial Policy for methodology, sourcing, and disclaimers.

Calculate your Body Mass Index from height and weight. Supports metric and imperial units with health category display. Methodology: BMI = weight (kg) ÷ height (m)². Categories (Underweight < 18.5, Normal 18.5–24.9, Overweight 25–29.9, Obese ≥ 30) follow the World Health Organization classification. BMI is a screening tool only — see our editorial policy for the medical disclaimer.

About this tool

Body Mass Index (BMI) is a widely used screening measure that relates body weight to height. Calculated by dividing weight in kilograms by height in meters squared, BMI provides a quick categorization into underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30+) ranges. Our BMI Calculator supports both metric (kg/cm) and imperial (lbs/ft-in) units, provides your BMI category with color-coded results, and includes health information about each category. While BMI doesn't account for muscle mass or body composition, it remains a useful first-step screening tool recommended by healthcare organizations worldwide.

How to use BMI Calculator

Select your preferred unit system: Metric or Imperial.
Enter your height in centimeters (or feet and inches).
Enter your weight in kilograms (or pounds).
View your BMI score and health category.

Tips & best practices

BMI is a screening tool, not a diagnostic measure of health.
Athletes may have high BMI due to muscle mass, not excess fat.
BMI categories: <18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, 30+ obese.
Consult a healthcare provider for comprehensive health assessment.

Common use cases

Quick health screening and weight category assessment.
Tracking BMI changes over time with diet and exercise.
Medical and insurance applications that require BMI.
Educational purposes in health and nutrition classes.

Privacy

This tool runs entirely in your browser. We do not upload, store, log, or process your input on any server. Open your browser's DevTools Network tab to verify — there is no outbound request with your data. See our Privacy Policy for details.

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