DEXA

DEXA (Dual-energy X-ray Absorptiometry, sometimes spelled DXA) is a low-dose medical X-ray scan that measures bone mineral density and soft-tissue composition. The reference clinical method for measuring body fat percentage at ±1-2% accuracy.

The scan takes 10-20 minutes; the radiation dose is roughly 1% of a chest X-ray (about a day of natural background radiation). Cost: $50-200 in most US markets, often not covered by insurance unless ordered for diagnostic purposes (osteoporosis screening, post-menopausal bone health).

DEXA distinguishes three tissue compartments: fat mass, lean mass (muscle + organs), and bone mineral content. The body-fat-percentage number reported is fat-mass divided by total mass. The regional breakdown (arms vs legs vs torso) is more clinically useful than the global average for tracking changes from training or weight loss.

For at-home body composition estimation, the US Navy tape method (used by our body fat calculator) reaches ±3% accuracy — close to DEXA at zero cost.