The best bathroom scales

The one specification worth paying for

A bathroom scale does one thing well and several things approximately. The thing it does well is weigh you, and the specification for that is accuracy — how close the reading is to the truth — and repeatability, which is whether it gives the same answer twice in a row.

Withings publishes 50 g for the Body Smart. Most makers publish nothing at all, or publish a graduation (the smallest increment displayed) and let you assume it means accuracy. It does not: a scale can display to 0.1 lb and be several pounds out.

If a listing does not publish an accuracy figure, you are buying a display resolution and hoping.

Body composition, honestly

Nearly every scale in this price bracket reports body fat, muscle mass and water percentage. Here is what is actually happening.

The scale sends a tiny current up one leg and down the other and measures the resistance. Fat, muscle and water conduct differently, so the resistance implies a composition. That is called bioelectrical impedance analysis, and it is a real technique.

The limitation is that the current takes the path of least resistance through your lower body and largely misses your torso, and the result is affected by hydration, when you last ate, exercise and skin temperature. Which is why the same person can produce noticeably different readings within a day.

No manufacturer on this site publishes an accuracy figure for any body-composition metric. We are not going to tell you those numbers are meaningless — as a trend measured under identical conditions they can be informative. We will tell you they are not a measurement in the way the weight is, and we will not pretend otherwise.

The floor matters more than the scale

This is the most common cause of a scale that seems wrong, and it is free to fix.

A scale measures the force on four load cells, one at each corner. That arithmetic assumes all four are on the same rigid plane. On a soft or uneven surface the load redistributes and the reading changes.

Use a hard, level floor. Tile over a solid subfloor is ideal.

Never weigh on a bath mat or rug. This is the big one. Anything compressible under the feet will change the reading, often by several pounds.

Use the same spot every time. Even on tile, a slight rock in one corner is consistent if the position is consistent.

Watch out for underfloor heating. Some scales specify an operating temperature range, and a warm floor sits at the edge of it. Nobody here publishes one.

If you have a stone bath mat, it is rigid rather than compressible — but it is still a second surface between the scale and the floor, and we would put the scale directly on the tile.

Weigh yourself properly or not at all

Body weight swings by several pounds through a normal day from food, drink and hydration. If you weigh at different times you are measuring that swing rather than any change in you.

Same time of day, first thing, after the toilet, before eating or drinking, without clothes. That removes almost all of the noise.

Look at the weekly trend, not the daily number. This is what a Wi-Fi scale is genuinely good for — it records every reading without you doing anything, so the trend line exists whether or not you paid attention on any given morning.

Two things nobody publishes

Maximum user weight. Withings publishes a 5–180 kg (9–396 lb) range for its Body scale, which is a different product from either on this page, and publishes nothing for the Body Smart or the Body Comp. If you are near any published limit, ask the manufacturer directly before buying.

Warranty. Neither product page states one. That is a notable absence on an electronic device that lives on a bathroom floor.

Both scales rate Safe on our install rating — they are battery-powered objects placed on a floor, with nothing mounted, nothing drilled and no mains connection anywhere near a wet room.