Find your Body Mass Index in seconds. This free BMI calculator works in metric or imperial units and shows your BMI, weight category and the healthy weight range for your height – a quick screening tool, not a diagnosis.
BMI is a general screening tool, not a diagnosis. It doesn’t distinguish muscle from fat. Talk to a healthcare professional about what’s healthy for you.
How BMI Calculator Works
This tool estimates your Body Mass Index, a simple screening number that compares your weight to your height. It’s the same formula clinics and public health guidelines use as a quick starting point, not a diagnosis of your body composition or health.
Formula: BMI = weight in kg ÷ (height in meters)^2. The calculator also finds your healthy weight range by solving that same equation for weight at BMI 18.5 and BMI 24.9. If you enter imperial units, height and weight are converted to meters and kilograms first.
- Height — your height in centimeters, or feet and inches in imperial mode
- Weight — your body weight in kilograms, or pounds in imperial mode
Example Scenarios
| Height (cm) | Weight (kg) | BMI (Category) |
|---|---|---|
| 165 | 50 | 18.4 (Underweight) |
| 160 | 55 | 21.5 (Healthy weight) |
| 170 | 70 | 24.2 (Healthy weight) |
| 175 | 80 | 26.1 (Overweight) |
| 180 | 95 | 29.3 (Overweight) |
| 190 | 110 | 30.5 (Obese) |
BMI Calculator FAQ
What BMI range counts as a healthy weight?
A BMI from 18.5 to 24.9 is generally classed as a healthy weight, below 18.5 as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These bands are broad population screening categories, not a personal verdict on your health.How is BMI calculated from height and weight?
BMI divides your weight in kilograms by your height in meters squared. If you use imperial units, the calculator converts pounds to kilograms and feet/inches to meters first, then applies the same formula so the result matches the metric calculation.Does BMI distinguish between muscle and fat?
No. BMI only uses total weight and height, so it can’t tell muscle from fat, bone density, or where fat is carried on the body. Two people with the same BMI can have very different body compositions.How is the “healthy weight for height” figure calculated?
The calculator rearranges the BMI formula to solve for weight at the lower (18.5) and upper (24.9) ends of the healthy range, using your entered height. That gives a weight span rather than a single target number.Is BMI accurate for athletes or very muscular people?
Not reliably. Because muscle is denser than fat, athletes and heavily muscled individuals often land in the “overweight” or “obese” BMI range despite having low body fat, so BMI can overstate health risk for this group.Can this calculator be used for children or teenagers?
This calculator is built for adults. Children and teens grow at different rates, so their BMI is interpreted using age- and sex-specific growth charts and percentiles rather than the fixed adult categories shown here.Related Calculators
If your BMI lands in a category that surprises you, try the ideal weight calculator for a second reference point based on height and sex, or the body fat calculator to see body composition rather than a weight ratio. Strength-focused users may also like the lean body mass calculator to estimate weight excluding fat.