BMI Calculator

Calculate your Body Mass Index and understand your weight category

Calculate Your BMI

Your Body Mass Index
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Calculate your BMI
Height --
Weight --
Healthy Range --

Your BMI Analysis

Enter your details above to see your BMI results and analysis.

Understanding BMI

Body Mass Index (BMI) is a simple calculation using your height and weight to estimate body fat. While not a direct measure of body fat, BMI correlates with more direct measures and provides a reliable indicator for most people. It's used to screen for weight categories that may lead to health problems.

How to Use This BMI Calculator

  1. Enter your height: Choose between centimeters or feet/inches and input your measurement.
  2. Enter your weight: Choose between kilograms or pounds and input your measurement.
  3. Calculate your BMI: Click the button to see your results instantly.
  4. Review your analysis: See your BMI value, weight category, and personalized health information.

Example: Sarah is 5'4" (163 cm) and weighs 140 lbs (63.5 kg). Her BMI is 24.0, which falls in the healthy weight range.

BMI Categories

BMI Classification
BMI RangeCategoryHealth Risk
Below 18.5UnderweightPossible nutritional deficiency
18.5 - 24.9Healthy WeightLow risk
25.0 - 29.9OverweightModerate risk
30.0 - 34.9Obese (Class I)High risk
35.0 - 39.9Obese (Class II)Very high risk
40.0 and aboveObese (Class III)Extremely high risk

How to Interpret Your Results

Note: BMI is a screening tool, not a diagnostic measure. Other factors like muscle mass, bone density, and body composition should also be considered.

How This Calculator Works

BMI is calculated by dividing your weight in kilograms by the square of your height in meters. The formula is the same for adults of all ages and both sexes. We handle all unit conversions automatically.

BMI = weight [kg] / (height [m] × height [m])

For imperial measurements (pounds and inches), the formula includes a conversion factor:

BMI = (weight [lbs] / (height [in] × height [in])) × 703

Limitations of BMI

While BMI is a useful screening tool, it has limitations:

For a more complete assessment, consider waist circumference measurements and body composition analysis.

Frequently Asked Questions

Is BMI accurate for everyone?
BMI is a useful population-level measure but has limitations for individuals. Athletes with high muscle mass may have a high BMI without excess fat. Older adults may have a normal BMI but high body fat percentage. It's best used as a screening tool alongside other measurements.
What's a healthy BMI for my age?
For adults 20+, the standard BMI categories apply regardless of age. For children and teens, BMI is age- and sex-specific and should be interpreted using growth charts from the CDC or WHO.
Why does BMI matter for health?
Higher BMI is associated with increased risk for numerous conditions including heart disease, type 2 diabetes, high blood pressure, certain cancers, sleep apnea, and osteoarthritis. Maintaining a healthy BMI can significantly reduce these risks.
Should I worry if my BMI is slightly overweight?
A BMI in the overweight range (25-29.9) suggests increased health risks, but individual factors matter. If you're muscular, have a healthy waist circumference, and are metabolically healthy, your risk may be lower. However, for most people, aiming for the healthy weight range is ideal.
How can I lower my BMI?
To lower BMI, focus on sustainable weight loss through a modest calorie deficit, regular physical activity, and behavior changes. Aim for 1-2 pounds per week. Building muscle through strength training can also improve body composition without necessarily changing BMI.
What's better than BMI?
While BMI is convenient, more precise measures include body fat percentage (via DEXA scan, BodPod, or skinfold measurements), waist-to-hip ratio, and waist circumference. These provide better insight into fat distribution and body composition.
Is BMI different for men and women?
The same BMI values apply to both sexes, but women naturally have higher body fat percentages than men at the same BMI. This is why women often appear "softer" at the same BMI as men.
How often should I check my BMI?
For most adults, checking BMI every 3-6 months is sufficient unless you're actively trying to change your weight. More frequent measurements may not show meaningful changes and could lead to unnecessary stress.
Should children use this calculator?
This calculator is for adults 20+. Children and teens should use age- and sex-specific BMI percentile calculators from the CDC or WHO, as their body composition changes dramatically with growth and development.

Beyond BMI: Other Important Health Metrics

While BMI is valuable, consider these additional health indicators: