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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Body Mass Index (BMI) is one of the most widely used health screening tools in the world. Calculated from your height and weight, it provides a quick estimate of whether you're in a healthy weight range. While BMI has well-known limitations — particularly for muscular individuals — it remains a useful entry-level metric for understanding your current health status.
What Is BMI?
BMI is calculated by dividing your weight in kilograms by the square of your height in meters:
BMI = weight (kg) ÷ height² (m)
| BMI Range | Category | Health Implication |
|---|---|---|
| < 18.5 | Underweight | May indicate nutritional deficiency or underlying condition |
| 18.5–24.9 | Normal weight | Associated with lowest risk of weight-related disease |
| 25.0–29.9 | Overweight | Slightly elevated risk of metabolic disease |
| 30.0–34.9 | Obese (Class I) | Elevated risk of type 2 diabetes, cardiovascular disease |
| 35.0–39.9 | Obese (Class II) | High risk — medical evaluation recommended |
| ≥ 40.0 | Obese (Class III) | Very high risk — specialist intervention often required |
BMI Limitations: What It Doesn't Tell You
BMI is a population-level screening tool, not a precise measure of individual health. Its key limitations:
- Doesn't measure body fat: A bodybuilder with 8% body fat may have the same BMI as someone with 30% body fat at the same height and weight. BMI cannot tell the difference.
- Ethnicity variance: Research shows that people of Asian descent face elevated health risks at lower BMI values. The World Health Organization recommends lower thresholds for Asian populations.
- Age variance: BMI may underestimate body fat in older adults who have lost muscle mass, and overestimate it in growing children and teenagers.
- "Skinny fat": A "normal weight" BMI with a high body fat percentage and low muscle mass carries similar metabolic risks to obesity.
What to Do After Calculating Your BMI
Your BMI gives you a snapshot, not a complete picture. The most useful next steps:
- Calculate your TDEE — Understanding how many calories your body burns daily is the foundation of any body composition goal.
- Set a calorie target — Use the Macro Calculator to find your ideal daily calorie and macro targets.
- Focus on body composition — The goal isn't just to change the number on the scale, but to build muscle and reduce body fat — which may not always be reflected by BMI alone.
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.