BMI Calculator
Calculate your Body Mass Index instantly. See your category and gauge, and understand what your BMI actually means.
Calculate Your BMI
| BMI | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5–24.9 | Normal Weight |
| 25.0–29.9 | Overweight |
| ≥ 30.0 | Obese |
Enter your height & weight
Your BMI will appear here
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What Is BMI?
BMI (Body Mass Index) is a simple screening tool calculated from your height and weight. It was developed in the 1830s by Lambert Adolphe Jacques Quetelet as a population-level measure — not as a clinical diagnostic tool for individuals.
Despite its limitations, BMI remains widely used in healthcare as an initial screening tool because it correlates reasonably well with body fat percentage at a population level and requires only two easily measured inputs.
BMI Categories
- Under 18.5: Underweight — may indicate malnutrition or other health concerns
- 18.5–24.9: Normal Weight — associated with the lowest risk of weight-related disease
- 25.0–29.9: Overweight — elevated risk for metabolic conditions
- 30.0 and above: Obese — significantly elevated health risk
BMI Limitations — What It Doesn't Tell You
BMI does not distinguish between muscle and fat. A muscular athlete may have a BMI of 28 (classified as "overweight") despite having very low body fat — while a sedentary person with a BMI of 23 may have a high body fat percentage and significant metabolic risk.
BMI also doesn't account for age, sex, ethnicity, or fat distribution. Visceral fat (fat around the organs) is significantly more dangerous than subcutaneous fat, and BMI cannot differentiate between them.
Use BMI as one data point among many — in combination with waist circumference, body fat percentage, and metabolic markers like blood glucose and triglycerides.
What to Do After Calculating Your BMI
If your BMI indicates you're outside the normal range, the most actionable next step is to calculate how many calories your body actually burns each day (TDEE) and set a realistic goal. A 300–500 kcal daily deficit combined with adequate protein intake is the evidence-based approach to sustainable fat loss.
Frequently Asked Questions
BMI (Body Mass Index) is a simple ratio of weight to height squared, used as a population-level screening tool to categorize weight status. A BMI below 18.5 is considered underweight, 18.5–24.9 is normal weight, 25.0–29.9 is overweight, and 30.0 or above is classified as obese. It does not directly measure body fat, muscle mass, or health.
No. BMI does not distinguish between muscle and fat. A highly muscular person may have an "overweight" or "obese" BMI despite having very low body fat. Conversely, someone with a "normal" BMI can have a high percentage of body fat ("skinny fat"). For a more accurate picture of body composition, consider waist-to-height ratio, body fat percentage measurement, or DEXA scan.
BMI is a starting point, not a diagnosis. If your BMI is outside the normal range, the most actionable next step is to calculate your TDEE and understand how many calories your body burns daily. From there, you can set a realistic calorie target and macro split aligned with your goal — whether that is losing fat, gaining muscle, or maintaining your current body composition.