BMI Calculator
Disclaimer: This BMI calculator is for informational and educational purposes only. It is not medical advice. BMI does not account for muscle mass, bone density, age, sex, or ethnicity. Always consult a qualified healthcare professional for health assessments and advice.
Calculate your Body Mass Index (BMI) to find out if your weight is in a healthy range. Enter your height and weight below and get your BMI score, category, and a visual gauge showing where you fall on the scale.
How BMI Is Calculated
Body Mass Index (BMI) is calculated using a simple formula that relates your weight to your height:
- Metric formula: BMI = weight (kg) / height (m)2
- Imperial formula: BMI = (weight (lbs) / height (in)2) x 703
For example, a person who is 5'9" (175 cm) tall and weighs 160 lbs (72.6 kg) has a BMI of approximately 23.6, which falls in the normal weight range.
BMI Categories
The World Health Organization defines the following BMI categories for adults:
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Obese (Class III): BMI 40.0 or higher
Limitations of BMI
While BMI is a useful screening tool, it has important limitations:
- Muscle vs. fat: BMI cannot distinguish between lean muscle mass and body fat. Athletes and bodybuilders may have a high BMI despite low body fat.
- Age and sex: Women tend to have more body fat than men at the same BMI, and older adults may have more body fat than younger adults.
- Ethnicity: Health risks associated with a given BMI may vary among different racial and ethnic groups.
- Fat distribution: BMI does not account for where fat is stored. Abdominal fat (measured by waist circumference) carries greater health risks than fat distributed elsewhere.
For a more comprehensive health assessment, consult a healthcare provider who can evaluate BMI alongside other measurements and risk factors.
Healthy Weight Tips
- Balanced diet: Focus on whole grains, lean proteins, fruits, vegetables, and healthy fats. Avoid excessive processed foods and added sugars.
- Regular exercise: Aim for at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous activity per week, plus strength training twice a week.
- Adequate sleep: Adults need 7-9 hours of quality sleep per night. Poor sleep is linked to weight gain and increased appetite.
- Hydration: Drink plenty of water throughout the day. Sometimes thirst is mistaken for hunger.
- Mindful eating: Pay attention to hunger and fullness cues. Eat slowly and avoid distractions during meals.
Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a numerical value calculated from your height and weight. It is used as a screening tool to categorize individuals as underweight, normal weight, overweight, or obese. The formula is BMI = weight (kg) / height (m) squared. While BMI is widely used by health professionals, it does not directly measure body fat or account for muscle mass, bone density, or distribution of fat.
What is a healthy BMI range?
According to the World Health Organization (WHO), a healthy BMI range is between 18.5 and 24.9. A BMI below 18.5 is classified as underweight, 25.0 to 29.9 is overweight, and 30.0 or above is considered obese. However, BMI is just one indicator of health and should be considered alongside other factors like waist circumference, diet, physical activity, and family history.
How accurate is BMI?
BMI is a useful population-level screening tool but has limitations for individuals. It does not distinguish between muscle and fat mass, so athletes or muscular individuals may have a high BMI despite low body fat. It also does not account for age, sex, ethnicity, or where fat is distributed. For a more complete health assessment, BMI should be used alongside other measurements like waist circumference, body fat percentage, and blood tests.
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = weight (kg) / height (m)^2. For imperial units, the formula is BMI = (weight in pounds / height in inches^2) x 703. For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9.
Does BMI apply to children?
BMI is calculated the same way for children and teens, but the interpretation is different. For people under 20, BMI is plotted on age- and sex-specific growth charts to produce a percentile ranking. A BMI at or above the 85th percentile but below the 95th percentile is considered overweight, and a BMI at or above the 95th percentile is considered obese. This calculator is designed for adults aged 20 and older.