BMI Calculator — Body Mass Index

BMI Calculator: Body Mass Index Made Simple

BMI is a quick screening tool, not a diagnostic. A professional athlete with a lot of muscle mass will show as overweight by BMI. An older adult with normal BMI but high body fat (sarcopenic obesity) will show as healthy. Use this as one data point alongside waist circumference, body fat percentage, and how you actually feel and perform.

The World Health Organization defines BMI categories as: Under 18.5 (Underweight), 18.5-24.9 (Normal weight), 25-29.9 (Overweight), 30+ (Obese). These cutoffs were established based on population data and are better predictors of population-level health risk than individual health. For a fuller picture, pair BMI with a waist-to-height ratio — aim to keep your waist measurement under half your height.