A bathroom body scale can have discrepancies of as much as 30%, but you should try to find a bathroom scale that is only off by 7% or less. That's why it's important to understand how accurate bathroom scales are to know which one to choose.

Personal digital scales are generally accurate enough for tracking weight trends, typically offering a margin of error between 0.1 kg and 0.5 kg (0.2 to 1.1 lbs) under ideal conditions. However, their precision is highly dependent on how they are used. To get the most accurate reading, the scale must be placed on a hard, level surface like tile or hardwood; using a scale on carpet can result in weight errors of 10% or more because the fibers absorb some of the pressure intended for the sensors. Furthermore, "smart" scales that measure body fat percentage using Bioelectrical Impedance Analysis (BIA) are much less reliable for body composition than they are for total mass, often varying based on your hydration levels. To ensure consistency, it is best to weigh yourself at the same time each day (usually first thing in the morning) and avoid moving the scale, as many digital models require recalibration (often done by stepping on and off once) after being moved to a new spot.