Metric and imperial
Switch between kilograms with centimeters and pounds with feet and inches. The form updates instantly.
BMI Calculator
Enter your height and weight to get your Body Mass Index, the WHO category you fall into, and the healthy weight range for your height. Switch between metric (kg, cm) and imperial (lb, ft, in) with one click. All math runs in your browser.
Guide
How to use the BMI Calculator
1
Pick your unit system
Toggle between Metric (kg and cm) and Imperial (lb, ft, in) at the top of the form. The inputs change to match.
2
Enter your weight and height
Type the numbers in the boxes. The result updates as you type, so you do not need to click anything.
3
Read the result and the gauge
You get your BMI number, the WHO category, the healthy weight range for your height, and a colored gauge showing where you sit on the BMI scale.
What is BMI and how is it calculated?
Body Mass Index (BMI) is a simple number that estimates whether your weight is in a healthy range for your height. The formula is your weight divided by your height squared. In metric units that is kg / m². In imperial units the formula is (lb / in²) × 703.
The World Health Organization splits BMI into four bands for adults: under 18.5 is underweight, 18.5 to 24.9 is healthy, 25.0 to 29.9 is overweight, and 30.0 or higher is obese. Most national health agencies (CDC, NHS, NIH) use the same numbers.
BMI is a screening tool, not a diagnosis. It does not measure body fat directly, so a muscular athlete may show a high BMI without excess fat, and an older adult may show a normal BMI while carrying low muscle mass. Treat the result as a starting point for a conversation with your doctor, not a final answer.
Benefits
Why this BMI Calculator
Live calculation
Result updates as you type. No submit button, no page reload.
Visual gauge
A color-coded bar shows where your BMI sits across the underweight, healthy, overweight, and obese bands.
Healthy weight range
See exactly which weight range counts as healthy for your height, and how far you are from it.
WHO categories
Categories follow the World Health Organization standard, the same one used by the CDC, NHS, and NIH.
Private and free
All math runs in your browser. Your numbers never leave your device. No signup, no rate limit.
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FAQ
BMI questions, answered
What is a healthy BMI for adults?
A BMI between 18.5 and 24.9 is considered healthy for most adults aged 20 and older. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or higher is obese. These ranges are set by the World Health Organization.
How is BMI calculated?
BMI is your weight divided by your height squared. In metric units that is kilograms divided by metres squared. In imperial units it is pounds divided by inches squared, multiplied by 703. This calculator handles the math automatically once you enter the numbers.
Is BMI accurate for everyone?
Not always. BMI does not distinguish between muscle and fat, so athletes and bodybuilders often score in the overweight or obese range without excess fat. Older adults can score within the healthy range while carrying low muscle mass. Pregnant and breastfeeding people, children, and teens need different thresholds. Treat BMI as a starting point, not a verdict.
Does this calculator work for children?
No. The categories shown are for adults aged 20 and older. Children and teens use age-and-sex-specific BMI percentiles, which need a different chart. For ages 2 to 19, use the CDC BMI-for-age percentile calculator on the official CDC website.
What is a healthy weight for my height?
The calculator shows the healthy weight range for the height you enter, on the result card. The lower bound corresponds to a BMI of 18.5 and the upper bound to 24.9. If you are above or below the range, the card also shows how much weight to gain or lose to reach it.
Is my data sent to a server?
No. The calculation happens entirely in your browser using JavaScript. The numbers you type never leave your device. Refresh the page and they are gone.