BMI Calculator — Calculate Your Body Mass Index Instantly

Your weight alone tells you very little. A 90 kg person who is 6'2" is in a completely different health category than a 90 kg person who is 5'4". That's exactly why body mass index exists — and why a reliable BMI converter matters more than stepping on a scale.

Calculate your Body Mass Index (BMI) instantly using metric or imperial units, standard WHO guidelines, formulas, and growth percentiles. Understand your weight category relative to height and explore its medical significance. Assess whether your weight falls into a healthy, underweight, overweight, or obese classification.

BMI 18.5–24.9 is considered a healthy range by WHO.

How to Use the bmi

Body Mass Index is a numerical value calculated from a person's height and weight. It is a fast, cost-free screening tool to categorize body weight and correlate health risks across large populations.

1Select your preferred units (metric or imperial).
2Enter your weight in kilograms or pounds in the first field.
3Enter your height in centimeters or feet/inches, and click calculate to view your score.

The Standard BMI Formula

The BMI calculation divides weight in kilograms by the square of height in meters. For imperial units, the result is multiplied by a scaling factor of 703 to match the metric scale.

Metric: BMI = weight (kg) ÷ height² (m²)
Imperial: BMI = (weight (lbs) × 703) ÷ height² (inches²)

Common Reference Values & Comparisons

Refer to this table to study common calculations, reference ratios, or performance profiles for this tool:

BMI Score Range	WHO Weight Classification
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obesity Class I
35.0 – 39.9	Obesity Class II
40.0 and above	Severe Obesity Class III
10th Percentile (Child)	Healthy Weight
90th Percentile (Child)	Overweight
98th Percentile (Child)	Obese
Average Global BMI	23.5 (Normal)

Frequently Asked Questions (FAQ)

Not equally. BMI is a population-level screening tool. It works reasonably well across large groups but can misclassify individuals — particularly highly muscular people, older adults with low muscle mass, and certain ethnic populations.

While BMI is an excellent starting point, it is not a diagnostic tool. If your BMI falls outside the normal range, it represents an invitation to discuss your overall wellness with a certified medical provider rather than a definitive diagnosis of health.

Related Tools

bmi calorie ideal weight