The number on a traditional scale tells you almost nothing useful about your health. It can't distinguish between muscle gain and fat gain, doesn't account for water retention and provides zero context for why that number fluctuates day to day.
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For people trying to build healthier relationships with their bodies, the singular focus on weight becomes reductive and often demoralizing. Smart scales shift the conversation by measuring body composition, like muscle mass, body fat percentage, bone density and hydration, giving you a more complete picture of what's actually happening inside your body.
In this article: RunStar Smart Scale 28, Etekcity Smart Scale and RunStar Scale 13
Smart scales aren't perfect, and they're not necessary for everyone. But for people who want to measure health improvements beyond BMI, these devices provide actionable data that traditional scales don't.
Smart scales use bioelectrical impedance analysis (BIA) to measure body composition beyond just weight. When you step on the scale barefoot, it sends a weak electrical current through your body via metal sensors or electrodes on the platform. Different tissues conduct electricity at different rates — muscle tissue, which contains more water, conducts electricity easily, while fat tissue resists the current. The scale measures how quickly the electrical signal travels and uses algorithms to estimate body fat percentage, muscle mass, bone density and water content.
More advanced models use multiple frequencies of electrical current or additional electrodes (like handles you grip) to improve accuracy by measuring different body segments separately.
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Smart scales provide useful trend data, but shouldn't be treated as perfectly precise measuring instruments. Bioelectrical impedance analysis can be affected by hydration levels, recent meals, exercise, skin temperature and even where you place your feet on the sensors.
A scale might show your body fat percentage as 25% one morning and 27% the next, not because you gained fat overnight, but because you weighed yourself at different times relative to drinking water or eating. The absolute numbers matter less than the trends over weeks and months.
Compared to clinical-grade body composition testing like DEXA scans or hydrostatic weighing, consumer smart scales can be off by several percentage points. However, clinical testing costs $50 to $150 per session and isn't practical for frequent monitoring. Smart scales can still show relative changes — if your body fat percentage reading drops from 30% to 27% over three months while your muscle mass increases, that trend likely indicates real progress even if the actual percentages aren't laboratory levels of precise.
RunStar Smart Scale 28 34% OFF
In the last month, 2,000 Amazon shoppers have bought this eight-electrode scale that includes a retractable handle with upper-body sensors for more comprehensive body composition analysis than platform-only models. It measures 28 different body composition metrics and measures upper and lower body separately for higher accuracy. One reviewer called this the “Rolls Royce of smart scales” and we have to agree. It goes beyond the usual blanket body composition analysis to track composition by area of the body. Our tester found it rewarding to be able to track muscle gains in specific parts of the body.
In the last month, 7,000 people have purchased this scale that syncs with Apple Health for integrated tracking alongside activity, sleep and nutrition data from other apps. It measures body fat, BMI, muscle mass and other composition metrics via a four-electrode platform.
Runstar Scale 13 30% OFF
You can use this scale without a smartphone — it features a large display showing primary metrics and tracks 13 body composition measurements including weight, body fat, muscle mass, bone mass and hydration. 7,000 Amazon shoppers have bought it in the last month.
iHome Digital Bluetooth Smart Scale 40% OFF
Bluetooth connectivity syncs this scale's measurements to the iHome app for tracking BMI, body fat and muscle mass trends, and its more affordable pricing compared to some models makes it a more entry-level option for many people — which is likely why it's sold 5,000 units in the last month alone.
RENPHO Smart Scale 13 20% OFF
The extra-large platform on this scale accommodates bigger feet and provides more stable footing. It also shows seven key metrics directly on the display, so you can track many metrics without having to use a phone or set up an app. It supports up to 500 pounds, a higher weight capacity than many smart scales. In the last month, 2,000 Amazon shoppers have bought one.
Garmin Index S2, Smart Scale 13% OFF
This scale integrates seamlessly with Garmin's ecosystem of fitness trackers, watches and the Connect app for unified health data and measures body fat, muscle mass, bone mass, body water percentage and more. It supports multiple user profiles that recognize individuals automatically.
RENPHO's popular entry-level smart scale tracks body fat, muscle mass, BMI and other metrics via a feature-rich app that integrates with Apple Health, Google Fit and Samsung Health. Our tester found this to be easy to set up, and tracking was on par with more expensive models in side-by-side comparisons. However, it does not provide body composition breakdowns per area of the body.
Prices listed reflect time and date of publication and are subject to change.
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