How a digital bathroom scale works - strain gauges!

[@mmghv]

I'm always fascinated with how small of a voltage difference these gauges produce and yet they are fairly accurate when amplified.

[@BenFinio]

Same! I was leaning on one gauge with all my upper body weight and could barely get it to change by a millivolt. So even roughly doubling my weight if I was standing on the whole thing, it'd be split across all four gauges, so if anything the change would be smaller.