BMI Calculator

How BMI Calculator Works

Body Mass Index (BMI) is a measurement that uses your height and weight to determine if your weight is in a healthy range. It's a simple screening tool that's widely used by healthcare professionals to assess whether a person has a healthy body weight for their height.

Our BMI calculator supports both metric and imperial units, making it accessible for users worldwide. The calculation is instantaneous and provides not just your BMI value but also the corresponding weight category and health implications.

Medical Disclaimer: BMI is a screening tool and not a diagnostic instrument. It doesn't measure body fat directly and may not accurately reflect health status for all individuals. Consult with healthcare professionals for personalized health assessments.

BMI Calculation Formula

Metric System

For weight in kilograms and height in meters:

BMI = weight (kg) / (height (m))²

Imperial System

For weight in pounds and height in inches:

BMI = (weight (lbs) / (height (in))²) × 703

BMI Categories

  • Underweight: BMI less than 18.5
  • Normal weight: BMI 18.5 to 24.9
  • Overweight: BMI 25 to 29.9
  • Obese: BMI 30 or higher

Examples

Example 1: Metric Calculation

Input: Weight = 70 kg, Height = 1.75 m

Calculation: BMI = 70 ÷ (1.75)² = 70 ÷ 3.06 = 22.9

Result: BMI 22.9 (Normal weight)

Example 2: Imperial Calculation

Input: Weight = 154 lbs, Height = 5 feet 7 inches (67 inches)

Calculation: BMI = (154 ÷ (67)²) × 703 = (154 ÷ 4489) × 703 = 24.1

Result: BMI 24.1 (Normal weight)

Example 3: Overweight Range

Input: Weight = 80 kg, Height = 1.70 m

Calculation: BMI = 80 ÷ (1.70)² = 80 ÷ 2.89 = 27.7

Result: BMI 27.7 (Overweight)

Frequently Asked Questions

Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat mass, so very muscular individuals may have a high BMI despite being healthy. It's also less accurate for children, elderly adults, and pregnant women.
What should I do if my BMI is outside the normal range?
If your BMI indicates you're underweight or overweight, consider consulting with a healthcare professional. They can assess your overall health, body composition, and provide personalized recommendations for diet and exercise.
How often should I check my BMI?
BMI changes slowly with weight fluctuations. Checking monthly or quarterly is usually sufficient unless you're actively trying to lose or gain weight under medical supervision.
Can BMI predict health risks?
BMI can indicate increased risk for certain health conditions like heart disease, diabetes, and high blood pressure. However, it's just one factor among many that influence health outcomes.
Are there different BMI standards for different ethnicities?
Some research suggests that health risks may occur at different BMI levels for different ethnic groups. For example, some Asian populations may have higher health risks at lower BMI values.

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