Common BMI Mistakes
Mistakes people make when calculating or interpreting BMI — from mixed units to over-trusting a single reading.
Reviewed Jan 15, 2025
Quick answer
The biggest BMI mistake is treating it as a body-fat measurement. BMI can't tell muscle from fat, so very muscular people often score 'overweight' even when they're lean.
Watch out for these
- Mixing units — height in cm but weight in lb.
- Using adult BMI ranges for children or teens.
- Reading one BMI as a verdict instead of a trend.
- Ignoring waist measurement, which adds important context.