BMI Calculator
Calculate your Body Mass Index to understand your weight relative to your height
What is BMI and how do you calculate it?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared: BMI = kg/m². A BMI of 18.5-24.9 is considered normal weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese.
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Create Free AccountWhat is BMI?
Body Mass Index (BMI) is a simple measure of body fat based on your height and weight. It's calculated by dividing your weight in kilograms by your height in meters squared. While BMI doesn't directly measure body fat, it provides a useful starting point for understanding whether your weight may be putting your health at risk. Healthcare professionals worldwide use BMI as a screening tool to identify potential weight-related health issues.
How is BMI Calculated?
The BMI formula is: BMI = weight (kg) / height (m)². For imperial units, multiply by 703: BMI = weight (lbs) / height (in)² × 703. The result falls into categories: underweight (below 18.5), normal weight (18.5-24.9), overweight (25-29.9), and obese (30 and above). These categories help indicate potential health risks, though individual factors like muscle mass and body composition should also be considered.
Limitations of BMI
While BMI is a useful screening tool, it has limitations. It doesn't distinguish between muscle mass and fat mass, so athletes or muscular individuals may have a high BMI despite being healthy. It also doesn't account for age, gender, ethnicity, or where body fat is distributed. For a complete picture of your health, consider BMI alongside other measurements like waist circumference, body fat percentage, and overall fitness level.
BMI vs BMR: What's the Difference?
BMI measures your weight relative to height to categorize your body size. BMR measures the calories your body burns at rest. BMI tells you if you're at a healthy weight; BMR tells you how much energy your body needs. Use both together for a complete picture of your health.
Frequently Asked Questions
What is a healthy BMI range?
A healthy BMI range is between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health problems. However, BMI is just one indicator and should be considered alongside other health markers.
Is BMI accurate for athletes and muscular people?
BMI can overestimate body fat in athletes and muscular individuals because it doesn't distinguish between muscle and fat mass. If you have significant muscle mass, consider using body fat percentage measurements for a more accurate assessment.
How often should I check my BMI?
Checking your BMI monthly is sufficient for most people. Since BMI changes gradually with weight changes, weekly checks are unnecessary. Focus on long-term trends rather than daily fluctuations.
What should I do if my BMI is too high or too low?
If your BMI falls outside the normal range, consult a healthcare professional. For high BMI, focus on a balanced diet and regular exercise. For low BMI, ensure adequate nutrition and caloric intake. A personalized workout plan can help you reach a healthy weight.
Does BMI differ by age and gender?
Standard BMI categories apply to adults aged 20 and older regardless of gender. For children and teens, BMI is calculated the same way but interpreted using age- and sex-specific percentiles. Older adults may have slightly different healthy ranges.