BMI Calculator
Calculate your Body Mass Index (BMI) to understand your weight status. Enter your height and weight to get your BMI score, weight category, healthy weight range, and personalized health insights. Perfect for tracking your fitness and health goals.
What Is BMI?
Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It is calculated by dividing a person's weight in kilograms by the square of their height in meters (kg/m²).
BMI is a useful screening tool for identifying weight categories that may lead to health problems. However, it is not a diagnostic tool. Factors such as muscle mass, bone density, overall body composition, and racial and ethnic differences can affect the relationship between BMI and body fat.
How Does the BMI Calculator Work?
The calculator uses the standard BMI formula:
Metric Formula:
BMI = weight (kg) ÷ height (m)²
Imperial Formula:
BMI = (weight (lbs) ÷ height (in)²) × 703
The calculator automatically converts between metric and imperial units.
After calculating your BMI, the tool classifies it into one of four categories:
- Underweight: BMI below 18.5
- Normal weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese: BMI 30.0 or higher
The calculator also provides your healthy weight range, BMI Prime (a ratio of your BMI to the upper limit of normal BMI), Ponderal Index, and an estimated body fat percentage.
Why Use This BMI Calculator?
- Dual Unit Support: Switch between metric (kg, cm) and imperial (lbs, ft/in) units.
- Visual BMI Scale: See where your BMI falls on a color-coded scale.
- Category Breakdown: View all BMI categories and their health implications.
- Advanced Metrics: Get BMI Prime, Ponderal Index, and estimated body fat percentage.
- Free & Private: No registration, no data storage.
Limitations of BMI
- Muscle vs. Fat: BMI does not distinguish between muscle and fat. Athletes may have a high BMI but low body fat.
- Age and Gender: BMI does not account for age or gender differences in body composition.
- Ethnicity: Some ethnic groups have different BMI-related health risk thresholds.
- Pregnancy: BMI is not accurate during pregnancy or lactation.
- Children and Teens: For individuals under 20, BMI percentile is used instead of the standard BMI category.
❓ BMI Calculator FAQ
What is BMI?
BMI (Body Mass Index) is a measure of body fat based on height and weight. It is calculated by dividing weight in kilograms by height in meters squared (kg/m²).
How do I calculate my BMI?
Enter your height and weight into the calculator and click "Calculate BMI." The tool will automatically compute your BMI using the metric or imperial formula based on your selected unit system.
What is a healthy BMI range?
A healthy BMI for adults is between 18.5 and 24.9. A BMI below 18.5 is considered underweight, 25.0 to 29.9 is overweight, and 30.0 or higher is obese.
What is the difference between BMI and body fat percentage?
BMI is a simple calculation based on height and weight. Body fat percentage is a more direct measure of body composition. BMI does not distinguish between muscle and fat, so athletes may have a high BMI but low body fat.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It does not account for muscle mass, bone density, age, gender, or ethnicity. For athletes, older adults, and some ethnic groups, BMI may not accurately reflect body fat.
What is a normal BMI for women?
The healthy BMI range for women is the same as for men: 18.5 to 24.9. However, women typically have a higher body fat percentage than men at the same BMI.
What is a normal BMI for men?
The healthy BMI range for men is 18.5 to 24.9. Men typically have lower body fat percentage than women at the same BMI.
What is the BMI formula in pounds and inches?
The imperial formula is: BMI = (weight in pounds ÷ height in inches²) × 703. For example, a person weighing 154 lbs and 69 inches tall: BMI = (154 ÷ 69²) × 703 = 22.7.
What is the BMI formula in kilograms and meters?
The metric formula is: BMI = weight in kilograms ÷ height in meters². For example, a person weighing 70 kg and 1.75 m tall: BMI = 70 ÷ (1.75)² = 22.9.
What is BMI Prime?
BMI Prime is the ratio of your BMI to the upper limit of the normal BMI range (25.0). A BMI Prime of 1.0 means you are at the upper limit of the normal weight range. Values below 1.0 are healthy, above 1.0 indicate overweight.
What is the Ponderal Index?
The Ponderal Index is an alternative to BMI that uses height cubed instead of height squared. It is less influenced by height and may be more accurate for very tall or short individuals. Formula: PI = weight (kg) ÷ height (m)³.
How do I calculate my healthy weight range?
A healthy weight range is calculated using the normal BMI range (18.5 to 24.9). For your height, multiply your height in meters squared by 18.5 and 24.9 to get the lower and upper limits of your healthy weight range.
What is a good BMI for my age?
For adults, the BMI categories are the same regardless of age. For children and teens (2-19), BMI is evaluated using percentiles based on age and sex, as body composition changes during growth.
Is BMI different for athletes?
Yes. Athletes and bodybuilders often have a high BMI due to increased muscle mass, which weighs more than fat. Their BMI may classify them as overweight or obese even though they have low body fat.
What is the BMI of a 5'9" male?
For a 5'9" (69 inches) male, a healthy weight range is approximately 125 to 168 lbs. BMI depends on actual weight: at 154 lbs, BMI = 22.7 (normal). At 180 lbs, BMI = 26.5 (overweight).
What is the BMI of a 5'4" female?
For a 5'4" (64 inches) female, a healthy weight range is approximately 108 to 145 lbs. BMI depends on actual weight: at 130 lbs, BMI = 22.3 (normal). At 155 lbs, BMI = 26.6 (overweight).
What are the health risks of being underweight?
Being underweight (BMI below 18.5) can lead to nutritional deficiencies, weakened immune system, osteoporosis, fertility issues, and increased risk of complications from surgery or illness.
What are the health risks of being overweight or obese?
Overweight (BMI 25-29.9) and obesity (BMI 30+) increase the risk of heart disease, type 2 diabetes, high blood pressure, stroke, certain cancers, sleep apnea, and joint problems.
How often should I check my BMI?
It's a good idea to check your BMI periodically, such as every few months or when you notice significant weight changes. Regular monitoring can help you track your health and fitness goals.
Is this BMI calculator free?
Yes, this calculator is completely free to use. No registration or personal data storage is required. All calculations are performed in your browser.