How Accurate is a Scale For Body Weight
                     How Accurate is a Scale For Body 
Weight? 
When you weigh yourself at home, in a gym or in a doctor's office, you probably step 
onto a standard spring scale. The dial on the side of the scale eventually points to a 
number line based upon calculations that use Hooke's law, which states that a given 
force (your weight) causes a certain amount of displacement of a mechanical system. 
Most newer scales have digital screens instead of a traditional dial, but they work 
the same way. The scales have a load cell that detects your weight, and the data is 
converted into a digital signal that moves a readout on a screen. 
The best scales for body weight will also offer more data than just your weight. 
These smart scales will let you track dimensions like body fat percentage, bone and 
muscle mass as well as other health metrics. They can even sync up with fitness apps, 
like Apple Health or Google Fit, to make it easier to monitor and track your progress 
over time. 
These more specialized scales typically use a technology called bioelectrical 
impedance analysis. When you stand on the scale, a small sensor sends an 
unnoticeable electrical current up one leg and down the other. It then measures the 
resistance that the current meets along the way, which is a direct indication of how 
much fat you have. Fat conducts electricity less easily than other components of the 
body, such as muscles, so a higher fat percentage will result in more resistance. 
However, this method can be inaccurate in a couple of ways. For example, if you're 
dehydrated, the scale will likely overestimate your fat percentage because water can 
interfere with the electrical current's travel up and down your legs. Additionally, the 
length of your legs can affect how long it takes for the electrical current to travel up 
and down your body. Having longer legs can increase the distance that the current 
must travel, which in turn can cause it to have a higher error rate. 
A scale's accuracy can vary by factors such as age, gender and hydration status. 
However, the most significant factor is its calibration. In fact, the National Institute 
of Standards and Technology reports that many of the scales that people purchase at 
pharmacies and supermarkets aren't accurate because they lack regular calibration. 
Luckily, some scales can help you avoid this problem by using Bluetooth and Wi-Fi to 
connect to your smartphone or tablet. The FITINDEX WiFi Bluetooth Body Fat Scale, 
for instance, scans your entire body upon stepping on the platform and displays all 
of your measurements right on its display as well as on a separate app. It also lets 
you add up to five users so the whole family can track their results, which is a nice 
bonus for busy households. The only knock we found on this particular model is that 
it's not very portable and can be a little cumbersome to set up. It also doesn't 
include a built-in battery, so you'll need to keep a backup charged.