Calculate your Body Mass Index instantly, with category classification and healthy weight range — in metric or imperial units.
A BMI between 18.5 and 24.9 is generally considered healthy for most adults, per WHO classification.
BMI is a useful screening tool but doesn't account for muscle mass or body composition, so it may be less accurate for athletes, elderly people, or pregnant women.
BMI = weight in kg ÷ (height in meters)². For imperial units, BMI = 703 × weight in lb ÷ (height in inches)².
It shows the weight range that would give you a BMI between 18.5 and 24.9, based on your entered height.
Body Mass Index (BMI) is a widely used screening measure that estimates whether a person's weight is healthy relative to their height. This calculator computes your BMI instantly in either metric (kilograms and centimeters) or imperial (pounds and feet/inches) units, and shows which of the four standard WHO categories your result falls into: underweight, normal weight, overweight, or obese.
In metric units, BMI is calculated as weight in kilograms divided by height in meters squared (kg/m²). In imperial units, the formula is adjusted with a conversion factor: 703 × weight in pounds, divided by height in inches squared. Both formulas produce the same BMI value for the same person — they're just different ways of expressing the same underlying weight-to-height-squared ratio.
BMI is a useful, quick screening tool precisely because it only requires height and weight, but it doesn't distinguish between muscle mass and fat mass. A muscular athlete can have a "high" BMI while carrying very little body fat, while someone with low muscle mass and high body fat could have a "normal" BMI despite carrying unhealthy levels of fat. BMI also doesn't account for fat distribution, age-related changes, or differences between individuals of different body frames. It's best used as a general population-level screening indicator rather than a definitive individual health diagnosis — a doctor or health professional can provide more complete context using additional measurements.
Alongside your BMI number, this tool calculates the weight range that would put you in the "normal" BMI category (18.5–24.9) at your current height. This can be a more actionable number than the BMI value itself, since it translates the BMI formula back into a concrete weight target in your usual units.
All calculations happen directly in your browser using JavaScript — your height and weight are never sent to a server or stored anywhere.
BMI was originally developed in the 1830s as the "Quetelet Index" and later adopted by the World Health Organization as a population-level screening tool because it only needs two easily measured inputs — height and weight — and correlates reasonably well with body fat percentage across large groups of people. Its simplicity is exactly why it's used in clinics, insurance assessments, and public health surveys worldwide, even though it has known limitations for individuals.
Where BMI only looks at the ratio of weight to height, other measures try to capture body composition more directly. Waist-to-hip ratio and waist circumference estimate abdominal fat, which is more strongly linked to cardiovascular risk than overall weight. Body fat percentage, measured by calipers, bioelectrical impedance scales, or DEXA scans, separates fat mass from lean mass entirely. These measures are more informative for athletes or anyone with an atypical muscle-to-fat ratio, but they require extra equipment that BMI doesn't — which is why BMI remains the fastest first-pass check.
If you lift weights regularly, track your BMI trend over time alongside a body fat percentage measurement rather than relying on BMI alone. A rising BMI from added muscle is a very different outcome than a rising BMI from added fat, and the two can look identical on this calculator. Many trainers use BMI only as a quick baseline check at intake, then switch to body fat percentage or progress photos for ongoing tracking.
People use this tool for searches like "what is my BMI," "ideal weight calculator," "BMI chart for adults," "am I overweight calculator," and "healthy weight range for my height." This calculator covers each of these with instant metric and imperial results.