BMI Calculator
Determine your weight category relative to your height with BMI.
BMI Calculator
Body Mass Index (BMI) is a quick screening tool that estimates whether your weight is in a healthy range for your height. Enter your height and weight and get your BMI instantly — plus what it means for your health.
How to Use This Calculator
- Select your unit system: imperial (lbs/inches) or metric (kg/cm).
- Enter your height.
- Enter your weight.
- Click Calculate to see your BMI and weight category.
BMI Formula
Metric: BMI = weight (kg) / height² (m²)
Imperial: BMI = 703 × weight (lbs) / height² (inches²)
BMI Categories (CDC/WHO)
- Under 18.5: Underweight
- 18.5–24.9: Normal weight (healthy range)
- 25.0–29.9: Overweight
- 30.0–34.9: Obese (Class I)
- 35.0–39.9: Obese (Class II)
- 40+: Extremely obese (Class III)
Example Calculation
Height: 5'10" (70 inches) | Weight: 185 lbs
- BMI = 703 × 185 / (70²) = 130,055 / 4,900 ≈ 26.5
- Category: Overweight
- Healthy weight range for 5'10": 129–173 lbs (BMI 18.5–24.9)
Limitations of BMI
- BMI doesn't distinguish between muscle and fat. A muscular athlete may have a "overweight" BMI despite low body fat.
- BMI may underestimate body fat in older adults who have lost muscle mass.
- It doesn't account for fat distribution — where fat is stored (belly vs. hips) matters significantly for health risk.
- Different BMI cutoffs apply for different ethnic populations (Asian populations have higher health risk at lower BMIs).
Common Mistakes to Avoid
- Using BMI as the sole health metric — It's a screening tool, not a diagnosis. A doctor considers BMI alongside waist circumference, blood pressure, cholesterol, and lifestyle.
- Comparing BMI across very different body types — A short, very muscular person and a tall, slender person might have similar BMIs despite very different body compositions.
Frequently Asked Questions
What is a healthy BMI?
18.5–24.9 is the WHO healthy range. However, some research suggests optimal health outcomes at 20–22 BMI. Consult your doctor for personal targets.
How can I lower my BMI?
A combination of a sustainable caloric deficit and increased physical activity. Reducing 500 calories/day creates approximately 1 lb/week weight loss. Use our Calorie Calculator to find your target intake.
Is BMI accurate for children?
Children use age- and sex-specific BMI percentile charts (not the adult categories). A child's BMI is compared to peers of the same age and sex, not fixed numerical thresholds.
What other measures should I track alongside BMI?
Waist circumference (health risk increases above 35 inches for women, 40 inches for men), waist-to-hip ratio, body fat percentage (use our Body Fat Calculator), and blood markers.
Conclusion
BMI is a useful first indicator of weight-related health risk — simple, quick, and widely used. Use it as a starting point, then consult health professionals for a complete picture of your health status.
Related: Body Fat Calculator | Ideal Weight Calculator | Calorie Calculator | BMR Calculator
Expert Note
BMI is a screening tool, not a diagnostic measure. It does not distinguish between muscle mass and body fat. Athletes may have a high BMI due to increased muscle, not fat.
