BMI Calculator

Body Mass Index is one of the most widely used health screening measurements in the world, employed by doctors, insurers, nutritionists, and fitness professionals to quickly classify weight relative to height. This BMI calculator supports both imperial (lbs and feet/inches) and metric (kg and cm) inputs, returning your BMI score, WHO weight category, and healthy weight range for your specific height in one step. The strength of BMI lies in its simplicity and universality — it requires no equipment, no lab work, and no medical training. Primary care physicians calculate BMI at nearly every annual physical and use it to guide conversations about weight management, cardiovascular risk, type 2 diabetes prevention, and metabolic health. Health insurance applications and clinical trial enrollment criteria also routinely use BMI as a primary qualifier. BMI is not without limitations. Because it relies only on height and weight, it cannot distinguish between lean muscle mass and body fat. A competitive athlete with very low body fat may register as Overweight or Obese by BMI alone. Conversely, a sedentary person with a normal BMI may carry a disproportionate percentage of body fat — a condition sometimes called normal weight obesity — while appearing healthy by this single metric. For this reason, BMI should be interpreted alongside other measures: waist circumference, waist-to-hip ratio, body fat percentage, blood pressure, and fasting glucose. This calculator clearly shows the healthy weight range for your exact height, giving you a concrete target rather than an abstract score.

BMI is calculated from height and weight using one of two equivalent formulas depending on the selected unit system. For metric inputs: BMI = Weight (kg) ÷ Height (m)². This divides your weight in kilograms by the square of your height in meters. For example, 75 kg at 1.75 m gives BMI = 75 ÷ (1.75²) = 75 ÷ 3.0625 = 24.5. For imperial inputs (lbs and feet/inches): BMI = (Weight in lbs ÷ Height in inches²) × 703. The constant 703 is a unit-conversion factor that produces the same numerical result as the metric formula when US units are used. A person weighing 170 lbs at 5 feet 10 inches (70 total inches) has BMI = (170 ÷ 4900) × 703 = 24.4. The calculator classifies the result into four WHO-defined categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), and Obese (30.0 and above). It also computes the healthy weight range for your specific height by reversing the formula — taking the BMI boundaries of 18.5 and 24.9, multiplying each by height in meters squared, then converting the result back to your preferred weight unit. This gives you a concrete minimum and maximum weight target rather than a single abstract BMI score. Both the BMI score and healthy weight range update dynamically as inputs change.