What Is BMI?
Body Mass Index (BMI) is a calculation that uses your height and weight to estimate body fat. The formula is simple: BMI = weight (kg) / height² (m²). Despite its simplicity, BMI has been used by healthcare providers worldwide for decades as a quick screening tool.
The BMI Categories
The World Health Organisation defines four BMI categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). These thresholds were established from population studies and are useful for population-level trends.
Limitations of BMI
BMI is a screening tool, not a diagnostic measure. It has several well-documented limitations. It does not distinguish between muscle and fat — athletes often have a high BMI despite low body fat. It does not account for age, sex, ethnicity, or bone density. It is also inaccurate for very short or very tall individuals.
Better Measures of Health
Waist circumference, waist-to-hip ratio, and DEXA scans give a more complete picture of body composition. For cardiovascular risk assessment, your doctor may also measure blood pressure, cholesterol, and blood glucose alongside BMI.
Using the BMI Calculator
Our BMI Calculator supports both metric (kg/cm) and imperial (lbs/ft) inputs. Remember that the result is one data point among many — always discuss health concerns with a qualified healthcare professional.
