Free BMI Calculator: Calculate Your Body Mass Index
Body Mass Index is a quick screening tool, but it doesn't tell the whole story. Calculate your BMI below—then learn why body fat percentage matters more.
Why BMI Isn't Enough
BMI was developed in the 1830s as a population-level statistical tool—not for individual health assessment. A 2016 study of 40,420 U.S. adults in the International Journal of Obesity found that nearly half of people classified as "overweight" by BMI were metabolically healthy, while over 30% of people with "normal" BMI were cardiometabolically unhealthy.
Doesn't Measure Body Fat
BMI can't tell the difference between muscle and fat. A bodybuilder and an overweight person can have identical BMI.
Ignores Fat Distribution
Where you store fat matters. Belly fat is more dangerous than fat elsewhere, but BMI doesn't account for this.
One-Size-Fits-All Categories
BMI categories don't adjust for age, gender, ethnicity, or individual differences in body composition.
Misleads Athletes
Muscular athletes often classify as 'overweight' or 'obese' despite having very low body fat and excellent health.
Calculate Your BMI Score
Your Measurements
Body Fat % is More Accurate
BMI can't see muscle
Two people with the same BMI can have very different body compositions. PhysiqueAI estimates what matters more—your body fat percentage.
- No tape measure or calipers needed
- Track progress over time with photo history
- Body fat, muscle, lean and fat mass estimates
- Works with mirror selfies
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BMI Categories (WHO)
BMI Category Ranges
BMI Formula
Metric Formula
BMI = weight (kg) / height (m)^2
Imperial Formula
BMI = (weight lbs x 703) / (height in)^2
Body Fat % vs BMI
BMI Tells You:
- Your weight relative to height
- A rough population-level category
- Nothing about actual body composition
Body Fat % Tells You:
- Actual fat vs muscle ratio
- Whether you're losing fat or muscle
- True health risk indicators
- Progress during body recomposition
BMI Calculator FAQ
What is BMI?
BMI (Body Mass Index) is a simple measure of body size based on height and weight. It's calculated as weight (kg) / height (m)^2. While commonly used, it has significant limitations.
How is BMI calculated?
BMI = weight (kg) / height (m)^2. For imperial: BMI = (weight lbs x 703) / (height inches)^2.
What are the BMI categories?
Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese Class I (30-34.9), Obese Class II (35-39.9), Obese Class III (40+).
Is BMI accurate?
BMI is a rough screening tool, not a diagnostic measure. It doesn't account for muscle mass, fat distribution, or individual differences. Body fat percentage is more accurate.
Why can BMI be misleading?
Two people with identical BMI can have very different body compositions. An athlete with high muscle mass may have a 'high' BMI but low body fat and excellent health.
What's better than BMI?
Body fat percentage, waist-to-hip ratio, and visual body composition analysis provide more accurate health assessments than BMI alone.
Go Beyond BMI
Estimate your body fat percentage, lean body mass, and muscle mass from a single photo. No measurements needed.
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