Common adult cutoffs are guidelines, not universal truth across ethnicities and builds.

Pediatric BMI uses age and sex percentiles—different from adult tables.

Rounding height or shoes-on weight skews results slightly.

BMI Calculator

Calculate your Body Mass Index and get personalized health insights

Calculate Your BMI

Unit System

Metric (kg, cm) Imperial (lbs, ft/in)

Weight (kg)

Height (cm)

Your Results

Enter your measurements to calculate BMI

What is BMI?

Body Mass Index (BMI) is a measure of body fat based on height and weight. It's a simple screening tool used to categorize weight status and estimate health risk. BMI is calculated using a person's weight and height and is expressed as a number (kg/m²).

BMI Formula

BMI = weight (kg) / height (m)²

BMI = (weight (lbs) / height (inches)²) × 703

The metric formula uses kilograms and meters, while the imperial formula uses pounds and inches.

BMI Categories

BMI Range	Category	Health Risk
< 18.5	Underweight	Increased risk
18.5 - 24.9	Normal Weight	Low risk
25.0 - 29.9	Overweight	Moderate risk
30.0 - 34.9	Obesity Class I	High risk
35.0 - 39.9	Obesity Class II	Very high risk
≥ 40.0	Obesity Class III	Extremely high risk

Important Notes

BMI is a screening tool, not a diagnostic measure. It doesn't directly measure body fat.
BMI may overestimate body fat in athletes and muscular individuals.
BMI may underestimate body fat in older adults and those who have lost muscle mass.
For children and teens, BMI is age and sex-specific and interpreted differently.
Consult with a healthcare professional for a comprehensive health assessment.

BMI calculator: screening tool, not a medical diagnosis

Body Mass Index relates weight to height for population-level screening. It does not measure body fat percentage, bone density, or athletic muscle mass—athletes may read “overweight” despite low body fat.

Consult healthcare professionals for personalized guidance, especially for children, older adults, and pregnancy.

Practical tips

Use consistent units (metric vs imperial) when comparing over time.
Track waist circumference alongside BMI for metabolic risk context.
Discuss sudden weight changes with a clinician.
Pair results with sleep and activity habits holistically.

Common questions

Healthy range?: Common adult cutoffs are guidelines, not universal truth across ethnicities and builds.
Children?: Pediatric BMI uses age and sex percentiles—different from adult tables.
Accuracy of inputs?: Rounding height or shoes-on weight skews results slightly.

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