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Calculates Body Mass Index.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
Body Mass Index (BMI) is a weight-for-height index calculated as weight (kg) divided by height (m²). It is used internationally to classify adult weight status: underweight (BMI <18.5), normal weight (18.5–24.9), overweight (25–29.9), and obesity (≥30), as defined by the World Health Organization. BMI is a screening tool, not a direct measure of body fat. It does not distinguish between fat mass and lean mass, so muscular individuals, athletes, and persons with high bone density may be misclassified. In elderly patients, reduced height from vertebral compression can artificially elevate BMI. BMI should not be used as the sole criterion for clinical decisions about weight management. It must be interpreted alongside waist circumference, metabolic markers, and the patient’s overall clinical context. For children and adolescents, age- and sex-specific BMI percentiles are required. In pregnancy, BMI interpretation requires separate guidelines. This calculator is intended for adult screening only and does not diagnose obesity or body fatness.
Specialty
General MedicineCategory
AnthropometryDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-06
Formula
Keywords
Normal Range
18.5–24.9 kg/m²
| Classification | Range |
|---|---|
Underweight | <18.5 |
Normal weight | 18.5–24.9 |
Overweight | 25–29.9 |
Obesity | ≥30 |
Calculates Body Mass Index (BMI) to screen for underweight, normal weight, overweight, and obesity categories.
BMI is calculated as weight in kilograms divided by the square of height in meters (BMI = weight (kg) / height (m)²). Since height is provided in centimeters, the calculator converts height to meters before squaring.
Body weight in kilograms used as the numerator in the BMI calculation.
Height in centimeters, converted to meters and squared in the denominator.
Common error: Forgetting to convert cm to m will give incorrect values.
BMI <18.5 is underweight. 18.5–24.9 is normal weight. 25–29.9 is overweight. ≥30 is obesity.
BMI is a widely used screening tool that correlates with metabolic risk. While not a perfect measure of body fatness, it provides a quick, inexpensive assessment that guides further clinical evaluation and intervention.
A 35-year-old woman weighs 68 kg and is 165 cm tall.
Inputs:
Expected Result: BMI = 68 / (1.65)² = 24.98 kg/m². This is at the upper end of normal weight, bordering on overweight.
BMI is a screening tool that estimates body fat using height and weight.
No. BMI is only a screening tool and should always be interpreted together with clinical findings.
Disclaimer: This calculator is intended for educational and clinical screening purposes only. BMI is a screening tool and does not diagnose body fatness or health. Clinical decisions should be based on comprehensive patient assessment.