BMI Calculator
Calculate your Body Mass Index and find out where you stand on the healthy weight spectrum.
<18.5Normal
18.5–24.9Overweight
25–29.9Obese
≥30
| Category | BMI Range | Status |
|---|---|---|
| Underweight | < 18.5 | Below Normal |
| Normal weight | 18.5 – 24.9 | Healthy |
| Overweight | 25.0 – 29.9 | Above Normal |
| Obese Class I | 30.0 – 34.9 | High Risk |
| Obese Class II | 35.0 – 39.9 | Very High Risk |
| Obese Class III | ≥ 40.0 | Extreme Risk |
Calculate your Body Mass Index (BMI) from height and weight, see your healthy weight range, and check where you fall on the standard BMI category scale.
How BMI Calculator Works
BMI is calculated as weight in kilograms divided by height in meters squared: BMI = kg ÷ (m × m). If you enter imperial units (pounds and feet/inches), the calculator converts weight to kilograms (× 0.453592) and height to meters before applying the same formula.
The result is compared against the World Health Organization's standard adult BMI categories: under 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obese (split into Class I, II, and III).
The "healthy weight range" result works the formula backwards, showing the weight range (for your entered height) that would fall between a BMI of 18.5 and 24.9.
See It In Action
Who Uses BMI Calculator and Why
- Getting a quick screening number before a doctor's visit, so you have context for a conversation about weight.
- Tracking how your BMI shifts over months of a fitness or nutrition program alongside other measurements.
- Checking the healthy weight range for your height when setting a realistic weight goal.
Mistakes to Avoid
- Treating a single BMI reading as a verdict on your health rather than one screening data point — the calculator itself notes it does not distinguish muscle from fat.
- Comparing your BMI directly to a child's or a pregnant woman's expected range — the standard adult categories used here do not apply to those groups.
- Re-entering height or weight in the wrong unit system (e.g. typing centimeters into a field expecting inches) and not noticing the result looks unusually high or low.
Tips for Best Results
- If you are very muscular or an athlete, look at the body fat or body type calculators alongside BMI for a fuller picture — BMI alone can misclassify a muscular build as overweight.
- Use the healthy weight range result rather than fixating on hitting one exact BMI number — anywhere within 18.5–24.9 is considered a normal range, not just the midpoint.
Fixing Common Problems
My BMI seems too high even though I feel fit and lean. — BMI cannot separate muscle from fat, so a muscular build with low body fat can still show an elevated BMI. Check the body fat calculator for a more direct estimate of your composition.
My result doesn't match a BMI I was told at a doctor's office. — Double-check that height and weight were entered in the same units the calculator expects, and that any measurements weren't rounded differently — small entry differences shift the result more than people expect.
Terms Explained
BMI Prime: Your BMI divided by 25 (the upper edge of normal) — a value under 1.0 means you're within or below the normal range.
Underweight/Normal/Overweight/Obese: The four broad WHO categories BMI is sorted into, based on fixed thresholds (18.5, 25, and 30) that apply the same way regardless of age or sex.