BMI Calculator
Compute your Body Mass Index (BMI) from height and weight. This tool also shows your BMI category and an estimated healthy weight range.
About This Calculator
How to Use
- Select your preferred unit system (Metric or Imperial)
- Enter your Height (in cm or ft/inches)
- Enter your Weight (in kg or pounds)
- Click Calculate to see your BMI and category
- Review your healthy weight range for your height
📚 Understanding BMI (Body Mass Index)
Body Mass Index (BMI) is a widely-used medical screening tool that estimates body fat levels based on your height and weight. Developed in the 1830s by Belgian mathematician Adolphe Quetelet, BMI remains one of the most common health indicators used by doctors, nutritionists, and health organizations worldwide.
BMI provides a quick assessment of whether your weight falls within a healthy range for your height. While it's not a direct measure of body fat, research shows strong correlations between BMI and body fat percentage, making it a useful screening tool for weight-related health risks.
Important: BMI is a general screening tool and may not be accurate for everyone, including athletes with high muscle mass, pregnant women, elderly individuals, or growing children. Always consult healthcare professionals for personalized health assessments.
🧮 BMI Formula & Calculation
The BMI formula varies by unit system:
BMI = weight (kg) ÷ (height (m))²
BMI = (weight (lb) × 703) ÷ (height (in))²
Example Calculation:
• Height: 170 cm (1.70 m) | Weight: 70 kg
• BMI = 70 ÷ (1.70)² = 70 ÷ 2.89 = 24.2 (Normal weight)
• Height: 5'7" (67 inches) | Weight: 154 lb
• BMI = (154 × 703) ÷ (67)² = 108,262 ÷ 4,489 = 24.1 (Normal weight)
📊 BMI Categories & Interpretation
BMI values are classified into the following categories by the World Health Organization (WHO):
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Malnutrition, osteoporosis |
| 18.5 - 24.9 | Normal weight | Low risk (healthy range) |
| 25.0 - 29.9 | Overweight | Increased risk |
| 30.0 - 34.9 | Obese (Class I) | High risk |
| 35.0 - 39.9 | Obese (Class II) | Very high risk |
| 40.0 and above | Obese (Class III) | Extremely high risk |
💡 Practical Use Cases
- Health Monitoring: Track your weight status over time and identify trends
- Fitness Goals: Set target weights based on healthy BMI ranges (18.5-24.9)
- Medical Screening: Initial health assessment tool used by doctors and clinics
- Insurance Applications: Some health and life insurance policies use BMI for rate calculations
- Nutrition Planning: Understand your baseline for creating personalized diet plans
- Weight Loss Programs: Establish starting point and track progress toward goals
- Sports & Athletics: Monitor weight categories for competitive sports
❓ Frequently Asked Questions
Is BMI accurate for everyone?
No. BMI is a general screening tool that works well for most adults but has limitations. It may not accurately reflect body composition for athletes with high muscle mass, bodybuilders, pregnant women, elderly individuals with reduced muscle mass, or growing children and adolescents. It also doesn't account for bone density, overall body composition, or racial and ethnic differences.
What is a healthy BMI range?
A healthy BMI typically ranges from 18.5 to 24.9 for adults. This range is associated with the lowest health risks and optimal longevity. However, individual health should be assessed holistically, considering factors like waist circumference, body composition, fitness level, and overall health markers.
How often should I check my BMI?
For general health monitoring, checking your BMI every 3-6 months is sufficient. If you're actively working on weight loss or gain goals, monthly checks can help track progress. More frequent monitoring (weekly) may be useful during intensive programs but remember that weight naturally fluctuates, so focus on trends rather than daily changes.
Can BMI predict health problems?
BMI is correlated with health risks but doesn't directly predict individual health outcomes. Higher BMI (≥25) is associated with increased risk of type 2 diabetes, heart disease, high blood pressure, certain cancers, and sleep apnea. However, many other factors influence health, including diet quality, physical activity, genetics, stress levels, and sleep patterns.
What if my BMI is outside the normal range?
If your BMI is below 18.5 or above 25, consult with a healthcare provider for personalized advice. They can assess your overall health, body composition, lifestyle factors, and recommend appropriate interventions if needed. Don't rely solely on BMI—consider it one tool among many for evaluating health.