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BMI vs Body Fat Percentage

BMI vs Body Fat Percentage

Section titled “BMI vs Body Fat Percentage”

BMI and body fat percentage are both “body composition” indicators, but they measure different things.

  • BMI estimates weight status using height and weight.
  • Body fat % estimates how much of your total weight is fat mass.

If you want a quick screening metric, BMI is often enough. If you’re trying to understand body composition changes (especially with strength training), body fat % can be more informative.

Use the tool: BMI Calculator

When BMI is useful

Section titled “When BMI is useful”

BMI tends to work well for:

  • Population-level screening
  • Quick health-risk categorization
  • Tracking large weight changes over time

BMI is less informative when you have a lot of muscle mass or unusual body proportions.

When body fat % is useful

Section titled “When body fat % is useful”

Body fat % tends to be more useful for:

  • People doing strength training or recomposition
  • Monitoring fat loss while maintaining weight
  • Comparing progress when the scale doesn’t change much

The accuracy depends heavily on the measurement method (calipers, BIA scales, DEXA, etc.).

Common mistakes

Section titled “Common mistakes”
  • Treating BMI as a diagnosis (it’s a screening metric)
  • Comparing body fat % from different devices/methods as if they’re identical
  • Ignoring waist circumference and health markers (blood pressure, labs, fitness)
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