# BMI Calculator > Calculate your Body Mass Index (BMI) in metric or imperial units with a live category gauge, healthy weight range, weight-to-goal, ideal-weight formulas, BMR, and waist-to-height risk — free. Enter your height, weight, age, and gender to get your BMI instantly, plotted on a colour-coded gauge from underweight to obese. Beyond the number, it shows your healthy weight range, how many kg or lb you'd move to reach it, three ideal-weight formulas, your daily BMR, and an optional waist-to-height risk score. Supports both metric (kg/cm) and imperial (lb/ft-in). - **Live tool:** https://www.toolnova.org/utilities/bmi-calculator - **Category:** Calculators & Converters (https://www.toolnova.org/utilities) - **Price:** Free - **Requirements:** Runs in a modern web browser · No signup · No install ## What this tool does - Metric (kg/cm) and Imperial (lb/ft-in) with automatic conversion - Live colour-banded BMI gauge with a moving marker - Healthy weight range and weight-to-goal (lose/gain) for your height - BMI Prime and daily BMR (Mifflin–St Jeor equation) - Ideal-weight estimates: Devine, Robinson, and Hamwi formulas - Optional waist-to-height ratio with risk classification - WHO BMI scale reference and honest limitations guidance ## How to use BMI Calculator 1. **Choose metric or imperial** — Switch the unit toggle to kg/cm or lb/ft-in. Any values you've entered convert automatically so you never lose your place. 2. **Enter height, weight, age and gender** — Use the sliders and fields. Age and gender refine the BMR and ideal-weight estimates. Optionally add your waist measurement for a waist-to-height risk read. 3. **Read your BMI and category** — The large number and the marker on the gauge show where you fall — underweight, healthy, overweight, or obese — against the standard WHO bands. 4. **Use the range and goal figures** — Check your healthy weight range and how much to lose or gain to reach it, then use BMR to plan calories. Treat all figures as screening estimates, not diagnosis. ## Common use cases - Checking whether your weight is in the healthy range for your height - Setting a target weight and seeing how far you are from it - Estimating daily calorie needs from BMR before dieting or bulking - Comparing metric and imperial results for a doctor or coach - Screening waist-to-height ratio as an extra cardiometabolic risk signal - Tracking BMI changes over a weight-loss or fitness programme ## About ### What BMI does and doesn't tell you BMI is a fast screening measure of weight relative to height, useful for spotting general trends across populations. It doesn't distinguish muscle from fat, so very athletic people can read as 'overweight' while the number is misleading — treat it as one signal, not a diagnosis. ### The BMI categories Standard ranges classify results as underweight, normal, overweight, or obese. These thresholds are the same worldwide for adults, which makes BMI a consistent reference point, but individual health depends on many factors BMI can't capture. ### BMI, ideal weight, and BMR Alongside BMI, an ideal weight range shows a healthy target for your height, and basal metabolic rate estimates the calories your body burns at rest — a practical foundation for planning nutrition and fitness goals. ## FAQ ### How do I calculate my BMI? Enter your height and weight. The BMI formula is: weight (kg) / height² (meters). In imperial: 703 × weight (lbs) / height² (inches). A BMI of 18.5-24.9 is considered healthy. ### What is a healthy BMI range? Underweight: below 18.5. Normal weight: 18.5–24.9. Overweight: 25–29.9. Obese: 30 and above. These are WHO guidelines for adults. BMI ranges for children differ by age and sex. ### Is BMI an accurate measure of health? BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so muscular athletes may show as 'overweight' even at low body fat. It's also less accurate for elderly people who lose muscle mass. Use BMI as a guide, not a diagnosis. ### What is the ideal weight for my height? For a healthy BMI of 18.5-24.9, your ideal weight range varies by height. Example: at 5'8" (173cm), the healthy weight range is approximately 125-163 lbs (57-74 kg). The calculator shows your specific range based on your height. ### What is Basal Metabolic Rate (BMR)? BMR is the number of calories your body burns at complete rest to maintain basic functions (breathing, circulation, organ function). It's the minimum calories needed per day. Multiply by an activity factor to find your daily calorie needs. ### What is the difference between BMI and body fat percentage? BMI uses height and weight only — it can't distinguish muscle from fat. Body fat percentage directly measures how much of your weight is fat vs. lean mass. A muscular athlete may have a 'overweight' BMI but a healthy 12% body fat. Body fat percentage is a more accurate health indicator but requires specialized equipment to measure. ### What is Basal Metabolic Rate? BMR is the number of calories your body burns at complete rest to keep basic functions running — a baseline for calculating daily calorie needs. --- ToolNova — free, privacy-first browser tools. Most tools process data locally on your device. See https://www.toolnova.org/llms.txt for the full directory.