Xiaomi's smart scales are no longer just a weight measurement device. They're now able to analyze body composition by showing percentages of fat, muscle mass, water level, and even bone tissue. But how can a small device on the floor determine how much fat your body has? The answer lies in the bioimpedance analysis (BIA) technology that most modern smart scales use, including the Mi Body Composition Scale 2, Xiaomi Smart Scale 2, and others.
In this article, we will go into detail about how bioimpedance works, what factors affect the accuracy of measurements, and why Xiaomi's weights may differ from those of medical equipment. You will also learn how to use the device correctly to get the most reliable results, and what mistakes users often make, if you doubt the readings of your weights or just want to understand the principles of their work, this material is for you.
What is Bioimpedance Analysis and How Does It Work?
Bioimpedance analysis (BIA) is a method of assessing body composition based on measuring the electrical resistance of the body's tissues, because different types of tissue conduct electrical current differently:
- 💧 Water and muscles are good conductors (low resistance) because they contain a lot of electrolytes.
- 🧈 Fat is a poor conductor (high resistance) because it has almost no water.
- 🦴 Bones - practically do not conduct current.
Xiaomi scales pass through the body a weak electric current of 50-100 kHz (absolutely safe for humans) and measure resistance (impedance) at different sites. Based on this data, the algorithm calculates the percentage of fat, muscle mass and other parameters. It is important to understand that the BIA does not measure fat directly, it estimates it indirectly, based on mathematical models and statistics.
The process looks like this:
- You stand on the scale with bare feet (a prerequisite for contact with electrodes).
- A weak current passes through the legs, which passes through the lower part of the body.
- Sensors measure resistance and send data to the Mi Fit or Zepp Life app.
- The algorithm analyzes impedance, your height, weight, gender and age, and then gives the final figures.
What data Xiaomi scales use to calculate the percentage of fat
To calculate the percentage of fat, Xiaomi weights are not enough just to measure impedance.
| Parameter | How does the result affect | Where it comes from. |
|---|---|---|
| Age. | With age, metabolism slows down, and the percentage of fat usually increases. | It is manually entered in the application when setting up a profile. |
| Paul | Men and women have different distributions of fat and muscle mass. | This is indicated when creating an account. |
| Growth | It is used to calculate body mass index (BMI) and adjust formulas. | It is manually entered or synced with other Xiaomi devices. |
| Weight. | The main parameter for all further calculations. | Measured by scales directly. |
| Impedance | The main “raw” indicator, on the basis of which fat is calculated. | Measured by the electrodes of the scale. |
Most Xiaomi scales use simplified formulas designed for the average user, which means the results may be less accurate for:
- 🏋️♂️ Athletes with high muscle mass (muscle conducts current better than fat, which can lower the percentage of fat).
- 👵 Elderly people (changes in the distribution of water in the body).
- 🤰 Pregnant women (hormonal changes and fluid retention).
💡
If you are engaged in strength training, select the "Athlete" mode in the application settings - this will help to adjust the calculation algorithm.
Measurement accuracy: how much can you trust Xiaomi weights
The issue of accuracy is the most controversial issue when using smart scales, and the manufacturer claims an error of ±5% for fat percentage, but in practice, the spread can be larger. Why?
⚠️ Note: Xiaomi scales are not medical equipment, their indicators are evaluative in nature and are designed to track dynamics, not to make diagnoses.
The main factors affecting accuracy:
- 💦 Hydration level: If you drink a lot of water before measuring, your body resistance decreases, and the scales can understate your fat percentage.
- 🍽️ Time of day and meals. In the morning after sleep, the results are more stable. After eating or exercising, the data may be distorted.
- 🧴 Skin condition: Dry or rough skin on the feet worsens contact with electrodes.
- 🔋 Battery charge. When the charge is low, the scales can work unstablely.
To verify the accuracy, you can compare Xiaomi’s weights with data from a professional body composition analyzer (such as InBody or Tanita), which generally ranges from 2% to 7% depending on the weight model and individual characteristics of the user.
How to check the accuracy of the scales at home?
Step-by-step: how to measure the percentage of fat
To minimize errors, follow these guidelines:
☑️ Preparation for measurement
The measurement process itself:
- Turn on the scales and wait for zeros to appear on the display.
- Stand on the platform with bare feet, spreading the weight evenly.
- Wait 5-10 seconds until the scales complete the measurement (usually an audible beep is heard).
- Check the results in the Mi Fit or Zepp Life app.
If the scales show an error or cannot measure body composition, check:
- 👣 Contact of the feet with electrodes (the feet should be dry but not too rough).
- 🔋 Battery level (at a discharge below 20%, failures are possible).
- 📱 Connection to the application (the scales must be synchronized with the smartphone).
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For maximum accuracy, take measurements under the same conditions, such as every morning after waking up and before breakfast.
Xiaomi weights comparison: which ones are more accurate?
Not all Xiaomi scales are equally accurate.
| Model | Number of electrodes | Accuracy of fat measurement | Additional functions |
|---|---|---|---|
| Mi Body Composition Scale 2 | 4 (2 on each leg) | ±5% | 13 Body Composition Parameters, Synchronization with Mi Fit |
| Xiaomi Smart Scale 2 | 4 | ±6% | Basic analysis, display illumination |
| Mi Smart Scale (First version) | 2 | ±8% | Only weight and BMI, without analysis of composition |
| Xiaomi Mi Body Fat Scale | 4 | ±5% | Support for the “Athlete” mode, memory for 16 users |
The most accurate results are given by models with 4 electrodes (two on each leg), as they allow you to more accurately estimate the distribution of current in the body. Libras with 2 electrodes (for example, the old Mi Smart Scale) measure only weight and approximate percentage of fat using a simplified formula.
If you want high accuracy, pay attention to the Mi Body Composition Scale 2 – this model is considered one of the best in the Xiaomi lineup in terms of price / quality.
Frequent User Mistakes and How to Avoid Them
Many complain about Xiaomi’s unstable weights, unaware that they are making mistakes, and the most common of them are:
- 🧦 Measurement in socks or shoes. Current must pass through the skin, so the legs must be naked.
- 🚿 Wet or sweaty feet, moisture can distort resistance, wipe your feet before measuring.
- 📵 No synchronization with the app, without gender, age and height, the weights will not be able to correctly calculate body composition.
- ⚡ Use on carpet or soft coating. Libra should stand on a hard surface (tiles, laminate).
⚠️ Warning: If you have recently been ill or are taking diuretics, your fat may be overestimated due to changes in water balance, in which case you should repeat the measurement in 2-3 days.
Another common problem is that there's a day-to-day jump in rates, which is normal if the difference is less than 1-2%, and if the percentage of fat changes by 5 percent or more in a day, check:
- The stability of the surface on which the scales are placed.
- Correctness of the entered data in the profile (height, age).
- Battery charge (with discharge, failures are possible).
Alternative methods of measuring body fat
If you doubt the accuracy of Xiaomi weights, you can use other methods:
- 📏 Caliperometry: measuring the folds of the skin with a stangentirculus at several points in the body: ±3–4%.
- 🧪 Hydrostatic weighing, immersion in water to assess body density, considered the gold standard, but requires special equipment.
- 📊 DEXA-X-ray method that gives the most accurate results (inaccuracy) ±1-2%), but expensive and inaccessible at home.
- 📱 3D-Body scanners, applications like Naked Labs or 3D Body Scanner builds body model from photos, but accuracy is lower than that of the BIA.
For most users, Xiaomi scales remain the best option due to their convenience and accessibility, and the main thing is to understand their limitations and use them to track dynamics, not to make medical diagnoses.