Health
BMI Calculator
Find your Body Mass Index and healthy weight range. Switch between imperial and metric in one click. No signup, no ads.
Your measurements
Enter your weight and height to see your BMI.
How is BMI calculated?
Body Mass Index
Variables
Body Mass Index-The calculated result, in kg/m^2
Weight-Your body weight in kilograms
Height-Your body height in meters
BMI Categories (WHO Classification)
| Category | BMI Range | Health Risk |
|---|---|---|
| Severe underweight | < 16.0 | High |
| Moderate underweight | 16.0 - 16.9 | Moderate |
| Mild underweight | 17.0 - 18.4 | Slightly increased |
| Normal weight | 18.5 - 24.9 | Low |
| Overweight | 25.0 - 29.9 | Slightly increased |
| Obesity Class I | 30.0 - 34.9 | Increased |
| Obesity Class II | 35.0 - 39.9 | High |
| Obesity Class III | >= 40.0 | Very high |
Frequently Asked Questions about the BMI Calculator
What is a healthy BMI for adults?
A BMI of 18.5 to 24.9 falls in the normal weight range for adults, per WHO guidelines. This calculator also shows the specific weight range that puts you in that zone for your height. BMI is a screening tool, not a diagnosis - it does not account for muscle mass, bone density, or where your body stores fat.
How is BMI calculated?
BMI equals your weight in kilograms divided by your height in meters squared (kg / m^2). In imperial units, the equivalent formula is (weight in pounds x 703) / height in inches squared. This calculator handles the unit conversion automatically - just enter your measurements and it applies the right formula.
Does BMI work the same for everyone?
No. BMI cannot distinguish muscle from fat, so a muscular person can read as overweight with no excess body fat, while an older adult who has lost muscle can read as normal despite elevated fat. Children and teens use age- and sex-specific percentile charts, not the adult cutoffs this calculator uses.
What should I do if my BMI is outside the healthy range?
Treat BMI as one data point, not a verdict. A doctor or registered dietitian can look at body composition, waist circumference, lab results, and family history to give you a fuller picture before recommending any changes.
Is BMI valid for athletes?
Often not. Muscle is denser than fat, so a heavily muscled person can land in the overweight range (BMI 25-29.9) or even obesity class I (30-34.9) with very little excess body fat. Body fat percentage and waist-to-hip ratio are better indicators for athletes.
What BMI is considered obese?
A BMI of 30 or above falls in the obesity range. The calculator uses three sub-classes: Class I is 30.0-34.9, Class II is 35.0-39.9, and Class III is 40 and above. It also flags severe underweight (below 16), moderate underweight (16-16.9), and mild underweight (17-18.4).
Does this calculator save my data?
Your inputs stay in your browser via localStorage. Nothing is sent to a server or shared with anyone. When you return to the page, the form re-fills with your last values automatically.
How accurate is this BMI calculator?
It uses the standard WHO formula and rounds results to one decimal place. Accuracy depends on how precisely you measure your weight and height - small errors in height matter more because height is squared in the formula. For example, at a BMI of 24, being off by 1 inch at 5 ft 10 in shifts your BMI by about 0.7 points.