How to calculate adult BMI in metric or imperial units
Formulas, WHO-style bands, and limits of BMI as a screening ratio — computed locally on Toolora.
Two formulas, one index
Metric BMI is kilograms divided by height in meters squared. Toolora asks for centimeters and divides by 100. Imperial BMI is the common US formula 703 × pounds / inches², with height in total inches (5′9″ is 69 inches, not 5.9). Switching the unit dropdown does not convert numbers already in the fields — re-enter values that match the labels. Example: 70 kg and 175 cm is about 22.9, labeled Normal on WHO adult bands. 90 kg at 170 cm is about 31.1, labeled Obese. Both weight and height must be greater than zero.
What the category labels mean
Under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese. Those cutoffs are population screens from WHO adult tables. They are not body-fat percentage, not fitness, and not a diagnosis. Athletes with high muscle mass, pregnant people, and many older adults sit in the “wrong” band relative to health. Pediatric BMI uses age-and-sex percentiles this tool does not compute — do not use it for children as if it were a growth chart.
Common mistakes
Entering feet in the inches box, mixing kg with inches, or treating BMI as a calorie target. The page does not estimate body fat, waist-to-hip ratio, or metabolic age. If a clinician asked for BMI, copy the number and the category, and bring the units you used. Nothing here is medical advice.
Privacy
Weight and height never leave the browser tab. Related: Percentage Calculator for generic ratios, GPA Calculator when the number you need is academic rather than physical. Close the tab to clear measurements. Common mistakes: feet in the inches box, mixing kg with inches, pediatric use, and treating the label as a diagnosis. Athletes and pregnancy commonly disagree with WHO adult bands. This is a screening ratio, not medical advice. Re-enter numbers after switching metric/imperial — the dropdown does not convert values already in the fields.