BMI Calculator - Calculate Your Body Mass Index (Metric & Imperial)
Calculate your Body Mass Index (BMI) instantly with our free BMI calculator. Determine if you're at a healthy weight with personalized health recommendations, weight categories, and BMI charts for adults.
Calculate Your BMI Instantly
Get your Body Mass Index in seconds
Your BMI
24.2
Normal
Scroll down for detailed analysis and health recommendations
What is BMI (Body Mass Index)?
Body Mass Index (BMI) is a widely used screening tool that measures body fat based on your height and weight. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI provides a simple numeric measure to classify individuals as underweight, normal weight, overweight, or obese. Healthcare professionals worldwide use BMI as an initial assessment tool to identify potential weight-related health risks.
The BMI formula divides your weight in kilograms by the square of your height in meters (kg/m²). For imperial measurements, the formula is: weight in pounds divided by height in inches squared, multiplied by 703. While BMI doesn't directly measure body fat percentage, research shows it correlates reasonably well with direct measures of body fat for most adults.
Our free BMI calculator supports both metric (centimeters and kilograms) and imperial (feet, inches, and pounds) units, making it easy for anyone to calculate their BMI quickly and accurately. Understanding your BMI is the first step toward maintaining a healthy weight and reducing risks of chronic diseases like heart disease, diabetes, and high blood pressure.
Your Measurements
Your BMI Results
Your BMI
24.2
Normal weight
Health Recommendation
Maintain your current weight through a balanced diet and regular exercise.
BMI Categories
How is BMI Calculated?
BMI calculation uses a simple mathematical formula that has remained consistent since its development. The calculation differs slightly depending on whether you use metric or imperial measurements:
Metric Formula
BMI = weight (kg) / height² (m²)
Example: A person weighing 70 kg and 1.75 m tall:
BMI = 70 / (1.75 × 1.75) = 70 / 3.06 = 22.9
Imperial Formula
BMI = (weight (lbs) / height² (in²)) × 703
Example: A person weighing 154 lbs and 69 inches tall:
BMI = (154 / (69 × 69)) × 703 = 22.7
Note: The number 703 in the imperial formula is a conversion factor that adjusts pounds and inches to match the metric BMI scale, ensuring consistent results regardless of which measurement system you use.
BMI Categories and Health Implications
| BMI Range | Category | Health Status | Health Implications |
|---|---|---|---|
| < 18.5 | Underweight | Below Healthy | Increased risk of malnutrition, weakened immune system, osteoporosis, and anemia |
| 18.5 - 24.9 | Normal Weight | Healthy | Lowest risk of weight-related health problems; optimal health range |
| 25.0 - 29.9 | Overweight | At Risk | Increased risk of heart disease, high blood pressure, type 2 diabetes, and sleep apnea |
| 30.0 - 34.9 | Obese Class I | High Risk | High risk of cardiovascular disease, stroke, certain cancers, and joint problems |
| 35.0 - 39.9 | Obese Class II | Very High Risk | Very high risk of serious health conditions; medical intervention often recommended |
| ≥ 40.0 | Obese Class III | Extremely High Risk | Extremely high risk; immediate medical attention and weight management program recommended |
Limitations of BMI
While BMI is a useful screening tool, it has several important limitations that you should understand:
Doesn't Measure Body Composition
BMI cannot distinguish between muscle mass and fat mass. Athletes and bodybuilders may have high BMI due to muscle, not excess fat.
Age and Gender Differences
BMI doesn't account for age-related muscle loss or gender differences in body composition. Women naturally have more body fat than men.
Ethnic Variations
Different ethnic groups may have different health risks at the same BMI. Asian populations may face health risks at lower BMI values.
Fat Distribution Not Considered
BMI doesn't indicate where fat is stored. Abdominal fat (visceral fat) is more dangerous than fat stored in hips and thighs.
Overall Health Picture
BMI doesn't consider other health factors like blood pressure, cholesterol levels, blood sugar, or family history of disease.
Not for Children or Pregnant Women
Standard BMI calculations don't apply to children, teenagers, or pregnant women. Special growth charts are needed for youth.
Frequently Asked Questions About BMI
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by your height in meters squared (kg/m²). For imperial units, divide weight in pounds by height in inches squared, then multiply by 703. Our calculator automatically performs this calculation for both metric and imperial measurements.
What is a healthy BMI range?
A healthy BMI for most adults ranges from 18.5 to 24.9. This range is associated with the lowest risk of weight-related health problems. However, individual health factors and body composition should also be considered when assessing overall health.
Is BMI accurate for everyone?
BMI is a useful screening tool but not accurate for everyone. It may overestimate body fat in athletes and muscular individuals, and underestimate it in older adults who have lost muscle mass. Pregnant women, children, and certain ethnic groups require different assessment methods.
Can BMI predict health problems?
BMI can indicate increased risk for certain health conditions like heart disease, diabetes, and high blood pressure. However, it's just one factor. Healthcare providers consider BMI alongside blood pressure, cholesterol, blood sugar, family history, and lifestyle factors for comprehensive health assessment.
What BMI is considered obese?
A BMI of 30.0 or higher is classified as obese. Obesity is further divided into Class I (30.0-34.9), Class II (35.0-39.9), and Class III (40.0 or higher). Each class represents increasing health risks and may require different treatment approaches.
How can I lower my BMI?
Lower your BMI through a combination of balanced nutrition and regular physical activity. Aim for a calorie deficit by eating nutrient-dense foods and exercising 150-300 minutes weekly. Gradual weight loss of 1-2 pounds per week is safest and most sustainable. Consult healthcare providers for personalized guidance.
Does muscle weigh more than fat?
Muscle is denser than fat, meaning it takes up less space for the same weight. A pound of muscle and a pound of fat weigh the same, but muscle occupies less volume. This is why BMI may be misleading for muscular individuals who may have high BMI but low body fat percentage.
What is the difference between BMI and body fat percentage?
BMI estimates body fat based on height and weight, while body fat percentage directly measures the proportion of fat in your body. Body fat percentage is more accurate for assessing health risks but requires specialized equipment like DEXA scans, bioelectrical impedance, or skinfold calipers.
Is BMI different for men and women?
The BMI calculation formula is the same for men and women, but women naturally have higher body fat percentages than men at the same BMI. Some health organizations suggest different BMI thresholds for men and women, though standard classifications remain widely used for both genders.
Should I use BMI or waist circumference?
Both measurements provide valuable health information. BMI assesses overall weight status, while waist circumference indicates abdominal fat distribution. Waist circumference over 40 inches for men or 35 inches for women indicates increased health risks. Using both measurements together provides a more complete health picture.
Tips for Achieving and Maintaining a Healthy Weight
Balanced Nutrition
Focus on whole foods including fruits, vegetables, lean proteins, whole grains, and healthy fats. Practice portion control and limit processed foods, sugary drinks, and excessive sodium intake.
Regular Exercise
Aim for at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous activity weekly. Include strength training twice weekly to build muscle mass and boost metabolism.
Lifestyle Habits
Get 7-9 hours of quality sleep nightly, manage stress through meditation or yoga, stay hydrated with 8-10 glasses of water daily, and avoid smoking and excessive alcohol consumption.