Scale Buying Guide
Scale Buying Guide
Weights and Measures

Today's bathroom scales do more than just tell you what you weigh. Many now determine the percentage of your weight that comes from fat. Some also calculate your body mass index, or BMI, which measures your weight in relation to your height. And several scales allow you to upload all that information to your smartphone or computer, so you can track changes in those body measurements over time and, if you choose, share it with friends.

All of the bathroom scales in the Ratings are digital, not analog. Many require a tap of the foot before you step aboard. One scale is solar, working with sun or artificial light, so it needs no battery. The other scales use lithium, AA, or AAA batteries and turn off automatically to prolong battery life. Most also have a low-battery indicator. All of the scales can handle at least 330 pounds; some can handle 400. 


How We Tested

To test the accuracy of the weight reading for scales, we used male and female volunteers. Panelists stepped on our calibrated lab scale and then on each of the test scales in random order. To assess how consistent readouts were, we had panelists of different weights climb on and off the scales.

Rating the body-fat scales was more complicated. They all measure body fat in the same way: When you step barefoot onto the device's metal footpads, a tiny electric current—much too low to feel—passes up one leg, through your pelvis, and down the other leg. The resistance that the electric current encounters depends on the proportion of fat and muscle tissue. Based on that, the scales use built-in formulas to estimate the percentage of your weight that comes from fat. To test the accuracy of the body-fat scales, we sent six volunteers—three men, and three women, some heavier, some more slim—to a university lab, where they climbed into an egg-shaped scientific instrument called a Bod Pod. That tightly sealed device determines body fat by precisely recording the volume of air a body (wearing tightly fitting clothing) forces out while sitting inside. Then we compared the results.

What We Found
The best bathroom scales were accurate within plus or minus 1 pound from 97 to 100 percent of the time, though one scale routinely overestimated weight by 6 to 10 pounds. All were at least very good at repeating the weight they'd measured. But none of the scales we tested were accurate for measuring body fat.

Bottom Line
All the digital scales that measure weight alone were accurate, so look mostly for the style and functions you like. Although the body-fat scales we tested weren't accurate at determining body fat percentage, they offer other features you might like, such as sending your measurements to your computer or smart phone so that you can keep track of your weight. The Ratings (available to subscribers) provide details.