Bathroom Scale Buying Guide

The manufacturers of a number of smart scales (and a few digital ones) claim that they measure the percentage of your weight that comes from body fat. How? When you step on the scale with bare feet, it passes a harmless electric current through your body. Fat and muscle conduct electricity at different rates; measuring those differences and using built-in algorithms to analyze the results allows the scales to estimate the percentage of your weight that comes from fat. They can also use this information to estimate the percentage of weight that comes from water, muscle mass, and bone mass. 

CR doesn’t routinely test the accuracy of body fat percentage measurements on scales that offer this. But in 2016 we did test a few consumer body fat scales and compared them with the results of a professional medical device designed to gauge body fat. We found that the scale results were off by 21 to 34 percent. 

More recently, in a study published in 2021, scientists in France tested three consumer body fat scales and found them to be accurate when measuring weight alone, but inaccurate when measuring body fat. In a review of the market for smart scales published in the International Journal of Medical Informatics, scientists in Norway recommended that consumers not rely on these scales for accurate absolute measurements of body composition, but rather as a way of tracking trends over time.

Capacity. Almost every scale in our ratings offers a maximum capacity of at least 396 pounds. Just two models have a smaller maximum capacity of 330. 

Surface size. Some users may find a scale with a wider surface more comfortable. (Look for “wide” in the model name.) You’ll also want to make sure your scale will fit in the spot where you’d like to keep it, so measure your space and check it with the product’s dimensions before you buy. 

App connectivity. For smart scales, you may prefer to sync your data with another health app like Apple Health or Google Fit. Our ratings list all the major health apps that sync with the scales we’ve tested. 

Accuracy. We use a calibrated lab scale that displays the correct weight to the hundredth of a pound as our reference. We weigh seven different amounts ranging from 25 to 200 pounds, and compare the readings from each bathroom scale with those of the lab scale.

Consistency. We take multiple readings of each weight on each scale and compare them. A high score on this test means that users can be confident that changes in the scale’s readings reflect real changes in weight, rather than random measurement error.

Unbalanced weighing. Our tester stands in different positions on each scale to see whether the readings change. This is useful for consumers who may have an uneven stance or an injury that prevents them from standing with even weight on both feet. 

Ease of use. We assess how easy it is to see the numbers on the display and adjust the scale to your preferences, and whether you can read the scale without turning on a light.

Smart IQ. For smart scales, we also evaluate connectivity, the ease of use of any product-specific application (for example, the Wyze app for Wyze scales), and extra features like whether a scale auto-saves, whether it has automatic weight tracking for tracking progress over time, and how long it takes for a reading to be displayed after the user steps onto it.