BMI Calculator
Calculate body mass index from height and weight, then compare the result with common BMI categories. BMI is a quick screening estimate, so use the guide below to understand both what it can show and what it cannot measure.
BMI Calculation Tips
BMI compares weight to height and is often used as a quick screening number. It can be helpful for a general snapshot, but it does not directly measure muscle, bone density, or body fat. Athletes and very muscular people may have a higher BMI without having the same health profile as someone with more body fat.
Quick Guide
- Use accurate height and weight.
- Remember BMI is a screening estimate.
- Consider waist size and fitness level too.
- Ask a professional for health decisions.
BMI Result
Compare height and weight to estimate body mass index.
Category Check
Review common BMI ranges while remembering they are screening categories.
Wellness Context
Use BMI with other measurements, fitness markers, and professional advice when needed.
BMI Formula
BMI stands for body mass index. In U.S. units, BMI = weight in pounds ÷ height in inches² × 703. In metric units, BMI = weight in kilograms ÷ height in meters². The result is a screening number that compares body weight with height.
Common Adult BMI Categories
| BMI Range | Common Category | Important Context |
|---|---|---|
| Below 18.5 | Underweight | May warrant nutrition or health review |
| 18.5 to 24.9 | Normal weight | Common healthy-weight screening range |
| 25.0 to 29.9 | Overweight | May need additional context such as waist size and fitness |
| 30.0 or higher | Obesity range | Often reviewed with other health indicators |
What BMI Can and Cannot Tell You
BMI can be useful as a quick population-level screening tool, but it does not directly measure body fat, muscle mass, bone density, waist circumference, cardiovascular fitness, or individual health risk. Athletes, very muscular people, older adults, and people with certain body compositions may need additional measurements.
Worked BMI Example
A person who weighs 180 pounds and is 70 inches tall has a BMI of about 25.8 because 180 ÷ 70² × 703 = 25.8. That result falls in the overweight screening range, but a complete health review would consider more than BMI alone.
Using BMI Responsibly
- Use accurate height and weight measurements.
- Do not use BMI as a complete health diagnosis.
- Consider waist circumference, body composition, activity level, and blood markers when relevant.
- Talk with a qualified professional for personal medical guidance.
- Track trends over time rather than obsessing over one number.
BMI Calculator FAQs
What does BMI mean?
BMI means body mass index. It compares weight with height using a standard formula.
Is BMI a body fat percentage?
No. BMI does not directly measure body fat. It is a height-to-weight screening estimate.
Can BMI be wrong for athletes?
Yes. Muscular athletes may have a higher BMI because muscle adds weight.
Is BMI used for children the same way?
Children and teens are typically evaluated using age- and sex-specific BMI percentiles, not the same adult categories.
What BMI is considered normal?
For many adults, 18.5 to 24.9 is commonly described as the normal-weight range.
Should I make health decisions based only on BMI?
No. Use BMI as one screening number and consult a qualified professional for medical decisions.