How To Tell If Your Scale Is Broken? –

How scales measure your body composition

Weight is simple enough: You step on the scale, and it measures the force with which gravity pulls down on your body.

The body fat, muscle mass, bone mass, body water, and other measures (which we can summarize as “body composition”) come from something called bioimpedance analysis, or BIA.

Conductive foot pads on your scale (which may be almost-invisibly layered into the material of the scale) pass a current through your body, from one foot to the other. You won’t feel this current, and it’s not dangerous, although if you have a pacemaker you may be told it’s best to turn this feature off.

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The scale can detect the electrical resistance between one foot and the other, which means the current is running up one leg, through your torso, and down the other leg. In essence, the formula imagines your legs and hips as a sort of horseshoe shape made of a mixture of water and not-water. It uses your height (which you enter into the app when you set up a profile) to guess at the length of this horseshoe shape. And based on the resistance it measures, it comes up with a guess about how much of your body is made of fatty tissues versus watery tissues.

As you might expect, there are many limitations to this approach. The biggest is just the number of guesses the formula has to make about your body to get from “this is a 5'6" human with a foot-to-foot resistance value of X” to “your body is 32% fat,” much less estimating the amount of bone or dry muscle tissue.


For example, it makes assumptions about how much of your fat, muscle, and so on are in your upper body versus your lower body. It can also be thrown off by how hydrated you are, how recently you have exercised, and whether you have artificial knees or hips.

A review article on the accuracy of BIA points out that, because so many assumptions are required, even the best devices and algorithms are probably never going to be able to give totally accurate, detailed body composition information for an individual:

A fundamental problem is that BIA is a predictive method that inherently requires simplifications and assumptions based on population mean values yet considered as being accurately applicable to all subjects.


A Consumer Reports study from 2016 found that the scales they tested differed from a BodPod measurement of body fat by anywhere from 21% to 34%. That’s not really accurate enough to know for sure what your body fat percentage is. If you truly want a number, any number, a simple calculation like the Navy body fat estimator is probably going to be just as good.

Some people say they like to watch their body fat (or muscle mass) change over time, and that it goes in the direction they’d expect. Your experience may vary on this. My Withings smart scale has never showed any meaningful change in these numbers for me, even when I know my body composition has changed. (And yes, I’ve tried turning on “athlete” mode. Even though I have more muscle than the average person my size, the numbers get even less realistic for me with athlete mode.)


Can I refuse to get weighed at the doctor?

You are allowed to refuse to be weighed. If the nurse insists, you can tell her to write “Patient declined to be weighed.” You can also say “I’d like to wait to see if it’s medically necessary based on the doctor’s assessment.” There were times during my recovery when it was helpful to do blind weighs.


How do I change my settings on my Weight Watchers scale?

Tap the scale to turn it on, and wait till “0.0” appears. Press the “User” button repeatedly until your user number shows on the display. 2. Stored data for your user number appears (User number, Height, and Age) then the scale displays “0.0”.

Do I Need Legal-for-Trade Calibration?

If you use your scale for commercial purposes, you need legal-for-trade calibration. For example, at the grocery store, your lunch meat and cheese is weighed on a scale and is sold to you at a price determined by that weight. That grocery store scale is an example of a commercial scale.

Commercial scales require legal-for-trade calibration. A state weights and measures inspector will follow up to ensure that your commercial scale has proper calibration.  A device found to be out of tolerance by a state inspector is generally tagged and taken out of service.  To avoid the problems associated with a device being found out of calibration by a state inspector, owners of commercial scales should have them calibrated and adjusted periodically to keep them in proper operating order.

How do I reset my Taylor Digital Scale?

The following reset procedure is used when the scale shows an err2, err, 0.0, inaccurate weight, or some other unusual error.
  1. Remove the battery from the scale.
  2. Sit the scale on a hard surface floor.
  3. Step up onto the scale, stand still for about 5 seconds and step off the scale.
  4. Re-install your battery.

Why is my weight different on different scales?

Why am I different weights on different scales

That’s because each brand of scale may have different calibrations, and some scales may be synchronized for your own body type or BMI. If they’re good scales, they’ll probably get an accurate reading that’s very close to your correct body weight.

How Do I Choose a Company to Calibrate My Scale?

All of this information won’t mean anything if it’s not documented and “traceable” to a primary standard. What does this mean, exactly?

Documentation is pretty straightforward. You must have a calibration certificate to show calibration results. If any part of the documentation isn’t there, the calibration is not traceable, and therefore, is like it never happened.

More importantly, it needs to be traceable to a primary standard. What is a primary standard? It’s the standard set by NIST. This does not mean you need to have your instruments calibrated by NIST, but it does mean that the company you use needs to have test standards that are calibrated by an unbroken chain of calibrations, traceable to NIST.  Using a calibration company that is accredited to the ISO 17025 standard provides this assurance of calibration traceability as well as proficiency in performing the calibrations.

Given the importance of this information, you can see why it’s advantageous to select a company that specializes in calibration — and why it’s so important to choose that company carefully.

There are two types of calibration companies — those that are accredited and those that are not. Why does it matter? The ones that are accredited are traceable.

That means you can be confident that the laboratory documents calibration results, has a system and procedure that is in working order and has employees that are educated and skilled in everything from the calibration process to the documentation of results. It also means that to keep their accreditation, they have to be audited on a regular basis and pass so that you can be confident in their technical proficiency and documentation abilities.

In addition to looking for an accredited calibration company, you want to make sure the team is educated and experienced in scale calibration and understands your process needs. Using Certified Weighing Technicians (CWT), certified by the International Society of Weights and Measures, provides you with the assurance that the technicians have the experience and knowledge necessary to perform expert calibrations. The CWT program requirements include years of experience in scale calibration, formal NIST H-44 training and passing a required written exam, and, to remain current, the technician must be re-certified every five years. The qualities you should look for in a CWT are superior documentation practices, attention to detail, honesty and integrity and understanding of the various calibration processes.

How accurate should your scale be? 

Of course, scales and measuring tools should always be accurate, but like every other object, they will capitulate to normal wear and tear and become unbalanced.  

Once your scale has become unbalanced, it needs to be recalibrated for accuracy. 

Why Scales May Not Be Accurate

Over time, scales can lose accuracy due to plain old wear and tear due to regular use and age. Scales must maintain their original balance for accuracy. Over time, however, they tend to lose this balance and they will require recalibration.

Electronic scales may suffer malfunction in the circuitry over time that can cause loss of accuracy. Even new scales may become inaccurate in certain conditions especially in extreme temperatures. For this reason, the most accurate scales will have high-temperature stability.

Additionally, new scales may lose accuracy in rough conditions especially when equipment is subject to vibration and jarring. In outdoor, industrial and similar environments, it is necessary to clean weighing equipment to maintain accuracy, especially for high precision work.

Eventually, scales even get dirty and potentially corroded. Cylinder scales should be made from a durable material like stainless steel, for instance. Those that aren’t will eventually start to suffer if they’ve been repeatedly exposed to fluids in the course of work. Those who work under certain specific conditions will also find that moisture levels in their home business community will cause similar problems.

For instance, think about a cosmetics facility that has to maintain a certain humidity level. This will surely start to eat away at scales that aren’t designed to remain durable against all odds. In some cases, only the most durable scales could ever be safely used anyway. This is because of of the presence of hazardous materials in a work environment.

You may want to learn how to test a scale. That way you won’t have to worry about whether or not any particular weighing device is showing the right weight.

Do they weigh you at the gynecologist?

A nurse or medical assistant will take you into the exam room to weigh you and get your blood pressure. If the doctor is going to do a quick visual check of things like breast growth, you will be left alone to get undressed.

Why do I weigh more but look thinner?

Since dense muscle tissue takes up less space than fat, it’s possible you may weigh the same (or even more) yet appear slimmer than another person with the same weight, a similar height and frame because of the difference in your body composition.”

How do I know if my scale is accurate?

For a reliable weight measurement, you may want to test your scale for accuracy. Wikihow has some great advice on how to test your scale to see if it’s giving you an accurate weight measurement. Recommendations include:

  • Zero out your scale before you weigh in.

    If you have a digital scale, it should zero itself, but if you’re using an analog scale, manually turn the dial to zero before you step on.

  • Weigh an object you know well.

    Is your five-pound sack of flour actually five pounds?

  • Weigh the same object more than once.

    Again, this speaks to scales reproducibility and precision, which we mentioned above: When you weigh the same object, how much do the measurements vary?

  • Weigh two objects.

    First, weigh them separately. Then weigh them together and check the combined weight. Do the numbers add up?

  • Change the scale’s location.

    Do the measurements change? For the most accurate measurements, we suggest weighing yourself in the same place every day, on a flat, hard surface.

If you’re looking for a roundup of the best bathroom scales, Verywellfit has a great list of the 5 best bathroom scales of 2020—including the best smart scale and the best scale for accuracy.

Tom’s Guide also offers suggestions for affordable and stylish options.

How Digital Bathroom Scales Work (And Fail)

Digital bathroom scales work in an entirely different way, and are generally considered more accurate and more reliable than a comparable mechanical scale. Of course, a truly high-tolerance mechanical scale can be extremely accurate, while a low quality digital scale can be just as variable as a mechanical box. So how does a digital scale work? They start with

So how does a digital scale work? They start with a small electronic item called a strain gauge. A strain gauge is a device that has been around since the late 1930s, and is really not a whole lot more than a carefully arrayed layer of metallic foil. This gauge is positioned on what is called a load cell, which also includes a sensor and a transducer.

When you step on the scale, your weight is evenly distributed across the surface, and you press down on the strain gauge. This converts your weight into an electrical signal. That signal is measured, and the circuits in the device convert that measurement into an accurate reading of the weight on the scale.

This allows a scale to be much more compact than a mechanical scale, while still maintaining reliability. It’s also the same system used in postage scales, which can measure in mere ounces reliably.

Electronic scales are accurate and reliable, assuming they were created and calibrated properly. Most electronic scales have a method in the instructions (possibly as easy as just stepping on and off) to “zero out” the scale. Zeroing the scale tells the scale what level of signal, or lack thereof, should be considered “zero”. After all, the scale’s surface has weight of its own that needs to be accounted for.In general, the circuitry in a digital scale will

In general, the circuitry in a digital scale will be reliable, though in ultra-cheap scales that might not be the case. The more common points of failure are in the parts themselves. Over time, circuits degrade, the load gauge can crack and fail, and parts can wear out. 

Can bathroom scales lose accuracy?

Yes. Age, wear and tear can take their toll on your bathroom scale.

Analog scales may be more prone to damage—for example, if the levers bend out of shape or if dirt gets into the springs.

Digital scales may be less likely to become contaminated. If you have a smart scale that’s connected to an app, make sure you install any suggested updates to keep your scale running smoothly.


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