How Xiaomi Smart Scales Determine the Percentage of Fat in the Body: Technology and Measurement Accuracy

Xiaomi’s smart scales are no longer just a weight measurement device. Today, they analyze body composition by showing percentages of fat, muscle mass, water level and even bone tissue. But how can a small device with four electrodes give such detailed information? In this article, we will examine the principle of bioimpedance analysis (BIA), which underlies all Xiaomi smart scales – from the budget Mi Body Composition Scale to the flagship Xiaomi Smart Scale 3.

Many users question the accuracy of such measurements, comparing them with professional methods such as hydrostatic weighing or sensing. DEXA-There is indeed a margin of error, but it depends a lot on the correct use of the device, and we will explain what factors affect the result, why readings may differ in the morning and evening, and how to minimize errors. And compare the algorithms Xiaomi with counterparts from Huawei and Withings – so you understand how universal the technology is.

If you've ever wondered why scales show different percentages of body fat after a workout, or why the Mi Fit app doesn't update immediately, the answers are below. We'll also look at hidden weight settings that are rarely mentioned in the manuals but affect accuracy, such as why it's important to tell your height to within a centimeter rather than rounding it to standard values.

Bioimpedance Analysis (BIA) Technology: How it Works

The basis for measuring the percentage of fat in Xiaomi scales is the bioelectric impedance analysis (BIA), the bottom line is simple: a weak electric current is passed through the body (usually 50–500 μA at 50 kHz), and sensors measure the resistance (impedance) of different tissues.

• 💧 Water and muscles are good conductors (low impedance).
• 🧈 Fat is a bad conductor (high impedance).
• 🦴 Bones - almost no current conducts.

Xiaomi scales use 4 electrodes: two on the platform for the legs and two on the handles (in models with manual analysis, for example, Xiaomi Body Fat Scale 2). Current passes from one leg to the other through the lower body, and in advanced models – also through the hands, which increases accuracy. The device algorithm analyzes resistance and based on the input data (sex, age, height) calculates the composition of the body.

It's important to understand that Xiaomi doesn't measure fat directly. Instead, it relies on empirical formulas developed from studies of thousands of people. For example, men and women use different ratios because they have different fat and muscle distributions. That's why it's so critical to specify the correct gender in the app, a mistake here will distort all other metrics.

What data is needed for the weight to accurately calculate fat

For the bioimpedance analysis to work properly, Xiaomi's weights require not only your body's resistance, but additional information, and without it, the algorithm will use averaged coefficients to increase the margin of error. Here are the mandatory parameters to set in the Mi Fit or Zepp Life app:

• 📏 Rounding to 170 cm instead of 168 cm can distort the percentage of fat by 1-2%.
• 👫 Women and men have different ratios of fat to muscle, even at the same weight.
• 🎂 Age. As you go through the years, your metabolism slows down, and fat percentages usually go up, and the algorithm takes that into account.
• 🏋️ Activity level (in some models) Athletes and people with high muscle mass receive adjusted data.

In addition, modern Xiaomi scales (such as Smart Scale 3) can ask for target weight and body type (ectomorph, mesomorph, endomorph), which helps to clarify the calculations, especially if your performance is beyond the “average” user. For example, a bodybuilder with a low percentage of fat and high muscle mass without these settings can get inflated fat values.

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If you do not know your exact body type, select the “Standard” option in the weight settings – the algorithm will automatically select the averaged coefficients.

Another nuance: Xiaomi scales don't measure visceral fat (the surrounding internal organs) directly, which is calculated based on total fat percentage and body mass index (BMI), so if your BMI is normal but your visceral fat is shown to be high, that's a reason to double-check other parameters or see a doctor.

Why Fat Indications Change During the Day

Many users have noticed that the percentage of fat on Xiaomi’s scales in the morning and evening can vary by 2-5%, which is normal and is due to physiological changes in the body.

• 💦 Hydration level. After sleep, the body is dehydrated, so the percentage of fat seems higher (water conducts current better, lack of water increases impedance).
• 🍗 After eating, blood rushes to the stomach, and the distribution of fluid in the body changes, which affects resistance.
• 🏃 After exercise, muscles are saturated with blood, and fat is temporarily diluted with water, the percentage of fat can decrease by 1-3%.
• 🌡️ Body temperature, hot weather or after sauna readings will be inflated due to water loss.

To get consistent data, measure body composition at the same time, preferably in the morning on an empty stomach and after using the toilet.

⚠️ Warning: If you drink alcohol the day before, your fat readings may be overestimated by 3 to 7 percent due to dehydration.

• ⏰ 2-3 hours after waking up (but before breakfast).
• 🚿 After showering (skin should be clean and dry).
• 🧘 Before training or 12.+ hours after.
• 🚫 No socks or tights (they increase resistance).

Fast morning|No shoes or socks.|With clean and dry feet|12 hours after training|At the same time every day-->

Comparing Xiaomi’s accuracy with medical methods

The bioimpedance analysis used in Xiaomi scales is inferior in accuracy to professional methods, but its error rate when used correctly is 3-5% - this is enough for home monitoring.

The key difference between Xiaomi’s weights and medical methods is that they only analyze the lower body (when measured without handles) or the lower + upper (in models with manual analysis), which means that the distribution of fat by zone (for example, belly fat vs. legs) is not taken into account, and the total percentage is calculated using average formulas.

To test your weights, you can compare them to caliperometry or bioimpedance analysis at a fitness club, a difference of 2-3% is considered normal, and if the difference is greater than 5%, check:

• 🔋 Charging of the scale battery (discharged elements can distort the signal).
• 📱 Firmware version (in Mi Fit update the device software).
• 🧍 Correctness of the entered data (height, weight, age).

Xiaomi’s Hidden Weight Settings That Affect Accuracy

Many users are unaware that Xiaomi scales have hidden parameters that can be customized to improve accuracy, such as the Mi Fit or Zepp Life app:

• 📊 Athlete mode (for people with high muscle mass) turns off automatic fat adjustment "in the direction of thinness".
• 🧬 Ethnic adjustment (in some models) takes into account the metabolic characteristics of different races.
• 🔄 Measurement frequency: You can choose how often the scales send data to the cloud (each weighing or once a day).

To activate these settings:

1. Open the Mi Fit app.
2. Go to Profile → Devices → [Your scales] → Settings for body composition analysis.
3. Turn on the option of Athlete Mode if your BMI is > 25 but your fat percentage is understated.

Another little-known fact is that Xiaomi scales calibrate automatically when first turned on, but can get lost over time. If you notice that readings have become unstable, reset:

1. Hold the power button for 10 seconds.


2. Wait for the indicator to flash.




3. Weigh again for a new calibration.

⚠️ Attention: If you use a scale on a carpet or soft coating, the sensors may not read resistance correctly. Always place the device on a hard, flat surface (tile, laminate).

Frequent User Mistakes and How to Avoid Them

Even the most accurate Xiaomi scales will lie if you break simple rules.-5 Mistakes that spoil the results:

• 🧦 Weighing in socks or tights: the fabric increases resistance, lowering the percentage of fat by 1-3%.
• 🕒 Measurement at different times of the day: Morning and evening data may differ by 5% due to changes in hydration.
• 💊 Ignoring drugs: Diuretics, steroids and even birth control pills affect water balance.
• 🔋 Batteries are dead, at voltage below. 2.7V The current becomes unstable, which distorts impedance.
• 🧴 Cream or sweat on the feet. Fat or sweat deposits on the skin increase resistance.

To check if your scales are lying, take a test:

1. Weigh yourself 3 times in a row at an interval of 1 minute.
2. Compare the fat readings. The difference should not exceed 0.5%.
3. If the spread is greater, clean the electrodes with alcohol and repeat the test.

FAQ: Answers to popular questions about Xiaomi weights

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For maximum accuracy, use Xiaomi’s manually analyzed scales (e.g., Xiaomi Body Fat Scale 2) – they take into account upper body impedance, which reduces the error by 1-2% compared to the foot-only models.