BMI Calculator
Body Mass Index from height and weight. Imperial or metric.
Your BMI
24.4
Normal
<18.5
18.5-24.9
25-29.9
≥30
A BMI calculator estimates your Body Mass Index, a single number from your height and weight that places you in a general weight category. It is a quick screening tool used widely in health settings.
Enter your height and weight in metric or imperial units. The tool returns your BMI and the standard category, from underweight through the overweight and obesity ranges.
BMI is useful as a rough guide for populations, but it does not measure body fat directly or account for muscle, so it is a starting point rather than a diagnosis.
How this calculator works
BMI is weight divided by height squared. In metric units it is kilograms divided by meters squared (kg/m2). In imperial units it is 703 times pounds divided by inches squared. The result maps to standard categories: below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or above is in the obesity range. These cutoffs come from population health data and are the same formula regardless of age or sex for adults, which is both its strength (simple and comparable) and its limitation (it ignores individual body composition).
What affects the number
- BMI uses only height and weight, so it cannot tell muscle from fat; very muscular people can read as overweight.
- It does not capture where fat is stored, though waist measurement and abdominal fat carry independent health signals.
- Standard adult categories do not apply directly to children and teens, who use age- and sex-based percentiles.
- Age, sex, and ethnicity affect the relationship between BMI and health, so cutoffs are general guides.
- Athletes and older adults are two groups where BMI most often misclassifies actual health.
- BMI is a screening number, not a diagnosis; a clinician considers it alongside other measures.
Frequently asked questions
What is a healthy BMI range?
For most adults, a BMI of 18.5 to 24.9 is considered the healthy-weight range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or higher falls in the obesity range. These are general screening categories, not individual diagnoses.
Is BMI accurate for athletes?
Often not. Because muscle weighs more than fat, muscular athletes can have a high BMI while carrying low body fat, so BMI can misclassify them as overweight. In those cases, body-fat measurements give a more accurate picture than BMI alone.
How do I calculate BMI manually?
In metric, divide your weight in kilograms by your height in meters squared. In imperial, multiply your weight in pounds by 703, then divide by your height in inches squared. This calculator does either instantly and shows your category.
Does BMI work for children?
Not with the adult categories. Children and teens are assessed using BMI-for-age percentiles that account for growth, sex, and age, because their body composition changes as they develop. A pediatric chart or clinician is the right reference for them.
This calculator provides general estimates for educational purposes only and is not financial, medical, legal, or tax advice. Your actual results depend on your specific situation and current rates.