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BMI Calculator

Body mass index with category rating

Body Composition
BMI Calculator
kg
cm

What This Calculator Measures

Body Mass Index (BMI) is a simple ratio of weight to height squared, used as a screening tool to categorize individuals into weight categories. It was developed by Adolphe Quetelet in the 1830s and remains the most widely used population-level measure of body composition.

Diagram showing how the BMI Calculator works
How the BMI Calculator works

How It Works

**BMI = Weight (kg) / Height (m)²**

For example, a person weighing 80 kg at 180 cm tall: BMI = 80 / 1.8² = **24.7** (Normal range).

BMI RangeCategory
Below 18.5Underweight
18.5 - 24.9Normal weight
25.0 - 29.9Overweight
30.0 and aboveObese

Context for Lifters

BMI is a useful population-level metric, but it has well-documented limitations for resistance-trained individuals. Because it does not distinguish between muscle and fat mass, a lean, muscular person can easily register as "overweight" or even "obese" by BMI standards while being in excellent metabolic health.

Limitations

•Does not account for muscle mass, bone density, or body fat distribution.
•A muscular 90 kg individual at 180 cm has a BMI of 27.8 ("overweight") despite potentially having 12% body fat.
•BMI is most useful for sedentary or general populations. For lifters, body fat percentage and waist-to-hip ratio are far more informative metrics.
•Does not reflect cardiovascular fitness or metabolic health.

Frequently Asked Questions

Is BMI actually useful for people who lift weights?
Not really. BMI doesn't distinguish between muscle and fat, so a muscular 200 lb guy at 5'10" gets classified as "overweight" even at 12% body fat. It's a population-level screening tool, not an individual fitness metric.
What BMI range is considered healthy?
The standard healthy range is 18.5-24.9. But if you lift weights, you'll likely be in the 25-28 range and perfectly healthy. Don't stress about BMI if you're training hard and your body fat percentage is reasonable.
Should I use BMI or body fat percentage?
Body fat percentage is far more useful for lifters. A guy at 15% body fat is in good shape regardless of what his BMI says. Use BMI as a rough screening tool and body fat percentage for actual fitness assessment.
Why do doctors still use BMI?
It's quick, cheap, and requires only height and weight. For sedentary populations, it correlates reasonably well with health risk. It just breaks down for anyone with above-average muscle mass, which is why lifters shouldn't take it too seriously.