Body Mass Index (BMI) Calculator
Enter your height and weight to calculate your Body Mass Index (BMI) and determine your weight category.
Your BMI: ' + bmi.toFixed(2) + '
'; resultHtml += 'Category: ' + bmiCategory + ''; resultHtml += 'BMI categories:'; resultHtml += '- ';
resultHtml += '
- Less than 18.5: Underweight '; resultHtml += '
- 18.5 – 24.9: Normal weight '; resultHtml += '
- 25.0 – 29.9: Overweight '; resultHtml += '
- 30.0 or greater: Obese '; resultHtml += '
Understanding Your Body Mass Index (BMI)
The Body Mass Index (BMI) is a simple numerical measure that is widely used to classify whether a person's weight is healthy in relation to their height. It's a screening tool that can indicate potential weight problems for adults, but it does not diagnose body fatness or health of an individual.
How BMI is Calculated
BMI is calculated using a straightforward formula:
BMI = weight (kg) / [height (m)]2
If you use pounds and inches, the formula is:
BMI = [weight (lbs) / (height (in))2] * 703
Our calculator handles these conversions automatically, allowing you to input your measurements in either metric (kilograms, centimeters) or imperial (pounds, inches) units.
BMI Categories for Adults
For adults aged 20 and older, BMI is interpreted using standard weight status categories:
- Underweight: BMI less than 18.5
- Normal weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 and 29.9
- Obese: BMI of 30.0 or greater
Why is BMI Important?
BMI is a useful indicator for several reasons:
- Health Risk Assessment: A high BMI can be an indicator of high body fatness, which can lead to various health problems such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.
- Population Health Monitoring: It's a simple and inexpensive screening tool for large populations to track trends in weight status.
- Personal Health Awareness: For individuals, it provides a quick snapshot of where their weight stands relative to their height, encouraging further discussion with healthcare professionals if needed.
Limitations of BMI
While BMI is a helpful tool, it has limitations:
- Muscle Mass: BMI does not distinguish between muscle and fat. Athletes or individuals with high muscle mass may have a high BMI but very little body fat, incorrectly categorizing them as overweight or obese.
- Age, Sex, and Ethnicity: BMI interpretations can vary based on these factors. For example, older adults may have less muscle mass than younger adults, and different ethnic groups may have different healthy BMI ranges.
- Body Fat Distribution: BMI doesn't account for where fat is stored. Abdominal fat (around the waist) is considered more dangerous than fat stored in other areas.
- Children and Pregnant Women: BMI is interpreted differently for children and teens (using growth charts) and is not typically used as a primary health indicator during pregnancy.
Example Scenarios:
Let's look at a couple of examples:
Example 1: Healthy Weight
A person is 175 cm (5 feet 9 inches) tall and weighs 70 kg (154 lbs).
Height in meters = 1.75 m
BMI = 70 / (1.75 * 1.75) = 70 / 3.0625 = 22.86
This BMI of 22.86 falls within the "Normal weight" category.
Example 2: Overweight
Another person is 160 cm (5 feet 3 inches) tall and weighs 75 kg (165 lbs).
Height in meters = 1.60 m
BMI = 75 / (1.60 * 1.60) = 75 / 2.56 = 29.30
This BMI of 29.30 falls within the "Overweight" category, nearing the "Obese" threshold.
It's important to remember that BMI is just one piece of the puzzle. For a comprehensive assessment of your health and weight status, consult with a healthcare professional who can consider other factors like body composition, diet, physical activity, and family history.