BMI Calculator

WHAT IT DOES BMI Calculator helps you understand your body mass index quickly and clearly. Enter your weight and height using either metric units (kilograms and centimeters) or imperial units (pounds and inches). The panel instantly displays your BMI value, your weight category (underweight, normal weight, overweight, or obese), and a visual scale that shows exactly where your result falls on the BMI spectrum. The color-coded scale provides immediate visual feedback, with blue for underweight, green for normal, yellow for overweight, and red for obese. This simple tool gives you a baseline understanding of your body composition in seconds. WHERE IT RUNS This script runs on every website you visit. Whether you are tracking your health on fitness sites, consulting medical information on health portals, monitoring your progress on wellness apps, or simply curious about your BMI while browsing, the panel is always available. It works alongside your existing tools without interfering with your workflow. HOW TO USE Select your preferred unit system from the dropdown menu — metric (kg/cm) or imperial (lbs/in). Enter your weight in the first field and your height in the second. Results update automatically as you type. The BMI value appears in large text at the top of the results area, followed by your weight category in the corresponding color. The visual scale shows your position relative to the standard BMI ranges. Click any history entry to reload previous calculations for quick comparisons. Use the "Copy Result" button to copy your BMI and category to your clipboard. THE STANDARD BMI FORMULA MECHANISM BMI Calculator uses the universally accepted formula established by the World Health Organization. For metric units, the formula is weight (kg) divided by height squared (m²). For imperial units, the formula is weight (lbs) divided by height squared (in²) multiplied by a conversion factor of 703. The calculator performs the calculation with floating-point precision, then rounds the result to one decimal place for display. The categories are determined using the standard WHO classification: underweight (< 18.5), normal weight (18.5 - 24.9), overweight (25 - 29.9), and obese (≥ 30). The visual scale positions your result along a continuous spectrum from BMI 10 to 45, providing a clear visual representation of where you fall relative to the category boundaries. THE PANEL The panel is fully draggable and remembers its position per site. It minimizes to a compact floating bubble when collapsed. All settings — unit preference and calculation history — persist across browser sessions using GM_setValue storage. Press the Escape key to close the panel. The panel automatically focuses the weight input field for quick keyboard entry. PLEASE NOTE This script requires the free BotGentz extension to run. BMI is a screening tool and does not diagnose body fatness or health. It does not account for muscle mass, bone density, age, sex, or ethnicity. Always consult with a healthcare professional for a complete assessment of your health. Websites change their structure and behavior over time; if any functionality stops working, the script may need an update. No user data is sent anywhere — all calculation history and settings are stored locally in your browser. The script never reads or modifies password, hidden, or file input fields.