BMI is a population statistic. Body fat is your personal reality. They agree on average and disagree on you specifically.
Some calculations matter for a single decision; this one matters for years. BMI is a population statistic. Body fat is your personal reality. They agree on average and disagree on you specifically.
Mass relative to height². It doesn't know muscle from fat. A bodybuilder and a couch-potato can have identical BMIs.
Fat mass ÷ total mass. Captures composition, which is what actually drives metabolic health.
Men: 10–20% healthy, 20–25% acceptable, 25%+ overweight. Women: 18–28% healthy, 28–32% acceptable, 32%+ overweight.
DEXA scan (gold standard, $50–150). Bioimpedance scale (cheap, ±5%). US Navy tape method (free, ±3%).
Why does BMI flag athletes as obese? Muscle is heavier than fat. BMI sees mass, not composition.
What's the leanest healthy body fat? Men around 8%, women around 18%. Below that, hormones suffer.
Whatever number you land on, sanity-check it against a second method or a quick estimate in your head.