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The Xiaomi Body Composition Scale S400 is a Bluetooth bathroom scale that estimates body composition using dual-frequency bioelectrical impedance analysis (BIA). It offers more than weight tracking, but its body-fat and other composition figures are estimates—not DEXA results or medical readings. Xiaomi cites a study reporting a strong correlation between selected fat-mass data and DEXA; that does not establish clinical equivalence. The bigger buying question is whether you are comfortable with Xiaomi Home and whether GeekWills is selling the regional model its listing describes: the retailer’s battery and connectivity claims conflict with Xiaomi’s global specifications.
What the S400 is—and what its name means
Xiaomi’s global product page calls it the Xiaomi Body Composition Scale S400; GeekWills lists a “Xiaomi Mijia Body Fat Scale S400.” Those names appear to refer to the S400, but the retailer’s listing does not establish that every regional specification matches Xiaomi’s global version. Confirm the model and packaging details with the seller before ordering.
Unlike a weight-only scale, the S400 uses sensors and an app-based profile to estimate a collection of body-composition measures. Its practical value is tracking patterns under repeatable conditions, not replacing a clinical assessment. Xiaomi describes its method and measurements on its official S400 product page.
How dual-frequency BIA works
Bioelectrical impedance analysis sends low-level electrical currents through the body and uses the resulting impedance readings, along with profile information such as height, age and sex, to estimate body composition. Xiaomi says the S400 uses 50 kHz and 250 kHz signals, associating the lower frequency with extracellular fluid measurement and the higher frequency with intracellular fluid measurement.
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#1 Best Overall
- Comprehensive 25 Body Composition Analysis: The Xiaomi Body Composition Scale S400 provides a detailed analysis of 25 essential body metrics, including body fat percentage, muscle mass, body water, protein, and bone mineral content. Gain deep insights into your physical condition to effectively manage your health and fitness goals with professional-grade data
- High Precision with Dual-Frequency BIA Technology: Experience exceptional accuracy with advanced Dual-Frequency Bioelectrical Impedance Analysis (BIA) technology. Key metrics, such as body fat percentage, are measured with a high correlation coefficient (≥0.93) against the DEXA gold standard, ensuring the data you receive is reliable and trustworthy for informed decision-making
- Smart Health Hub for the Whole Family: This smart scale automatically recognizes and stores data for up to 36 different users, making it perfect for family use. Each member gets a personalized profile within the Mi Home app, allowing everyone to track their unique health trends without data mixing
- Clear LED Display & Seamless App Integration: The scale features a bright, hidden LED screen that shows key readings like weight and heart rate instantly. For a complete overview, with the Mi Home app to view detailed historical trends, receive health insights, and connect with other Xiaomi ecosystem devices
- Versatile Weighing Modes & Practical Design: Beyond standard weighing, this scale offers specialized modes for various needs, including a mode for measuring babies or pets. Its large, non-slip platform (300x300mm) ensures stability, and the sleek, tempered glass design fits seamlessly into any bathroom decor
Using two frequencies may provide more information than a basic single-frequency, foot-to-foot scale. It still does not directly image or weigh fat, muscle, bone or organs. Values such as visceral-fat rate, muscle mass and bone-mineral mass are model estimates, not direct laboratory measurements.
What the 25 indicators tell you
Xiaomi lists 25 indicators in the S400 report. Weight is the most direct reading; many other values are derived estimates, and some are app-generated coaching outputs.
| Indicator | How to interpret it |
|---|---|
| Weight | Scale weight; generally the most straightforward measurement. |
| Heart rate | A static reading after body-fat measurement, not a heart-health assessment. |
| BMI | Weight relative to height; it does not distinguish fat from muscle. |
| Body score | Algorithmic summary score. |
| Body-water mass | Estimated body-water quantity. |
| Body hydration percentage | Estimated share of body weight represented by water. |
| Body-fat percentage | Estimated proportion of body weight that is fat. |
| Fat mass | Estimated total fat mass. |
| Protein mass | Estimated protein-related body-composition value; not a dietary protein measurement. |
| Protein percentage | Estimated proportion attributed to protein. |
| Muscle mass | Estimated muscle mass, not a direct measurement of individual muscles. |
| Muscle percentage | Estimated proportion attributed to muscle. |
| Bone-mineral mass | Estimated bone-mineral value, not a bone-density scan. |
| Bone-mineral percentage | Estimated proportion attributed to bone minerals. |
| Visceral-fat rate | Algorithmic estimate; not an image or diagnosis of abdominal fat. |
| Basal metabolic rate | Estimated resting energy expenditure. |
| Lean body mass | Estimated body mass excluding fat. |
| Body type | Algorithmic category based on reported measurements. |
| Estimated waist-to-hip ratio | Estimate, not a tape-measured waist-to-hip ratio. |
| Body age | Algorithmic comparison, not a measure of biological age. |
| Skeletal-muscle mass | Estimated skeletal-muscle value. |
| Weight control | App-generated guidance relative to a calculated target. |
| Muscle control | App-generated guidance, not a prescribed training plan. |
| Fat control | App-generated guidance, not a medical recommendation. |
| Standard weight | Calculated reference value rather than an individually established health target. |
For most users, weight and the direction of longer-term changes are easier to interpret than a single body-age, visceral-fat, protein or bone-mineral figure. Treat the derived values as estimates and use them alongside other information—not as stand-alone health findings.
Rank #2
- 𝑼𝒏𝒑𝒂𝒓𝒂𝒍𝒍𝒆𝒍𝒆𝒅 𝑨𝒑𝒑 𝑬𝒙𝒑𝒆𝒓𝒊𝒆𝒏𝒄𝒆: Elevate your fitness journey with us. Our scale stands out with the free vesync app, offering a customized diet and exercise plans based on your life habits. Achieve your fitness goals scientifically with ease (FSA/HSA eligible)
- 𝑼𝒑𝒈𝒓𝒂𝒅𝒆 𝑷𝒓𝒆𝒄𝒊𝒔𝒊𝒐𝒏: Benefit from our 10 years of professional experience and join over 5 million satisfied customers across 30 countries, our scale boasts high-precision sensors for accuracy in increments as small as 0.05 lb
- 𝑽𝒆𝒓𝒔𝒂𝒕𝒊𝒍𝒆 𝑾𝒆𝒊𝒈𝒉𝒊𝒏𝒈 𝑺𝒐𝒍𝒖𝒕𝒊𝒐𝒏: Our scale offers 3 different modes designed to cater to all your needs. Zero-Current Mode ensures a safe weigh-in option, Baby Mode tracks baby or pet growth, and For Light Items weighs items as light as 100g
- 𝑼𝒔𝒆 𝒘𝒊𝒕𝒉 𝑬𝒂𝒔𝒆: Seamlessly integrate our scale into your fitness routine. Compatible with APPLE WATCH and syncs data with popular fitness apps like Apple Health, Samsung Health, Google Fit, FitBit, and MyFitnessPal. Supports unlimited users for convenience
- 𝑾𝒆𝒊𝒈𝒉 𝑺𝒎𝒂𝒓𝒕𝒆𝒓: Beyond analyzing 13 biometrics, setting goals, and viewing progress graphs, our scale offers even more intelligence. Connect the app to Alexa for hands-free voice control and quick answers. Rest assured, VeSync prioritizes your privacy
How to interpret Xiaomi’s DEXA comparison
Xiaomi reports a correlation coefficient of at least 0.93 between the scale’s fat-mass data and DEXA in a study identified as report BSU20220389, conducted by researchers at the China Institute of Sport and Health Science at Beijing Sport University. That supports an association between measurements in that particular test; it does not mean every S400 reading will be within 7% of DEXA, validate all 25 indicators, or make the scale interchangeable with a DEXA examination.
GeekWills uses the phrase “comparable to DEXA” in its listing. That is the retailer’s characterization, not a basis for treating the scale as a clinical scan. Xiaomi says the S400 is not a medical device and its results are for reference. Do not use its readings to diagnose or treat obesity, fatty liver disease, cardiovascular conditions or other illness, or treat its heart-rate feature as a way to identify heart problems.
Specifications and limits
| Item | What is listed | Qualification |
|---|---|---|
| Measurement method | Dual-frequency BIA at 50 kHz and 250 kHz | Xiaomi’s description; composition values are estimates. |
| Weight range | 0.1–150 kg | Xiaomi-listed scale range. |
| Body-composition profile limits | Approximately 20–150 kg, 90–220 cm and ages 6–80 | Xiaomi-listed limits for body-fat measurement. |
| Age use | Body-composition functions for ages 6–80 | Children under 6 and adults over 80 can measure weight only; adolescent composition results are for reference. |
| Profiles | Up to 36 users | Recognition may fail when users’ weights are within ±2 kg; manual profile selection may be needed. |
| App | Mi Home/Xiaomi Home | Xiaomi says it is not compatible with Mi Fitness or other apps. |
| Minimum software listed | Android 8.0+ or iOS 12.0+; Xiaomi Home app Android 8.7.703+ or iOS 8.7.204+ | Check current regional app requirements before purchase. |
| Connectivity | Bluetooth; optional Bluetooth gateway for automatic synchronization when the phone is not directly connected | Xiaomi global specification. GeekWills lists Wi-Fi and Bluetooth; confirm the exact unit rather than assuming native Wi-Fi. |
| Battery | Three AAA batteries; up to 180 days | Xiaomi’s claimed maximum under its stated test conditions. GeekWills instead lists three AA batteries and about 360 days with once-daily use. |
| Retailer SKU | XMFS400 | GeekWills listing; confirm against the package and regional model details. |
| Price and stock | $49.90; “In stock” | GeekWills status observed August 18, 2026; price and availability can change. |
Xiaomi also lists small-object precision of 0.1 kg. Objects under 10 kg are treated as small objects; items weighing 10 kg or less are not saved as ordinary body-composition measurements. For objects of 5 kg or less, first wake the scale by stepping on it. This can help weigh an infant, pet, luggage or package, but it is not a substitute for a calibrated shipping or veterinary scale. The small-object and baby/pet modes are selected through the app.
Rank #3
- Large Screen Display: 5.3" color screen to instantly display 8 key metrics: weight, BMI, body fat, muscle mass, water, visceral fat, bone mass, and body type. Our weight scale fits all foot positions securely, with the compact 11"x11" sturdy platform
- Precision Measurement & Safety Design: Our body weight scale provides 0.1 lb/0.05 kg increments and supports weights up to 400 lb/180 kg, designed to provide consistent weight readings when used on a hard, level surface. Complementing its technical performance, the 5mm tempered glass platform and anti-slip textured surface provide enhanced stability and safety for users of all ages and fitness levels, from adults to athletes
- 14 Key Body Metrics & Health Analysis: This GE body fat scale measures 14 essential health indicators including weight, body type, body fat, BMI, skeletal muscle, muscle mass, protein, BMR, fat-free body weight, subcutaneous fat, visceral fat, body water, bone mass and metabolic age. The data empowers you to create personalized fitness plans based on detailed body composition trends
- Track Progress & Reach Goals: Our Digital bathroom scales with free Fit Profile app monitor your weight, muscle mass, and body fat using easy-to-read charts and historical data over days, weeks, or years. Additionally, this weight scale for body has the goal-setting feature, allowing you to set and review progress targets
- Multi-User & Fitness App Integration: The bluetooth body scale accommodates unlimited users while maintaining individual profiles for personalized tracking. It seamlessly syncs with the free Fit Profile app, Apple Health, Samsung Health, Health Connect and Fitbit, allowing easy sharing of body composition trends with loved ones
App compatibility, pairing and synchronization
Xiaomi’s stated app is Mi Home/Xiaomi Home, not Mi Fitness. Xiaomi also says the S400 is not compatible with other apps. If Apple Health, Google Fit, Health Connect, Fitbit, Garmin or another dashboard is essential, verify a supported integration before buying; do not assume one from the scale’s Bluetooth connection.
Pair the scale
- Gently step on the scale to wake it.
- Open the Mi Home/Xiaomi Home app.
- Tap the “+” icon in the upper-right corner.
- Select “Add a device.”
- Choose “Xiaomi Body Composition Scale S400.”
- Select the device, tap “Connect device,” and complete pairing.
Ordinary Bluetooth use and automatic cloud synchronization when your phone is elsewhere are different things. Xiaomi says the latter requires a separately purchased Bluetooth gateway. A “Bluetooth gateway not connected” message does not necessarily mean the scale’s direct Bluetooth connection is broken. If you have a gateway, Xiaomi advises waiting 1–5 minutes and rebooting it if it still does not connect; without one, the message can generally be ignored.
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- Confirm Bluetooth is enabled and the phone and Xiaomi Home app are up to date.
- If the scale is already listed in the app, delete that device entry.
- Open the battery cover and press the reset button with an ejection pin for 7 seconds.
- Repeat the add-device pairing process. If it still fails, update or reinstall the app and try again.
Family profiles and other modes
Xiaomi says the scale supports up to 36 users. Automatic recognition can be unreliable when two users’ weights are within ±2 kg, so select the right profile manually when necessary. The scale also offers visitor mode, in which the measurement is not saved, as well as baby/infant, pet, small-object and balance-testing modes. Modes are switched through Xiaomi Home; do not expect every function to be available from the scale alone.
Rank #4
- Smart App Sync & Fitness Integration: Easily connect your digital scale for body weight to the RENPHO Health app via Bluetooth. Sync your data seamlessly with fitness apps like Apple Health, Samsung Health, and Fitbit. (FSA eligible HSA)
- Track Progress & Stay Motivated: In addition to 3 metrics displayed—weight, BMI, and body fat—this bathroom scale also measures 13 key body metrics. All data is stored in the app, enabling you to view your progress daily, weekly, and monthly.
- Getting into the Habit of Health with RENPHO Smart Scale: Serving as your personal health manager, the RENPHO Health app builds a comprehensive health ecosystem – tracking your body metrics, calorie consumption, dietary intake, hydration levels, and more.
- User & Family‑Friendly Design: Set up in minutes with the RENPHO Health app, compatible with Apple Watch, and supports unlimited users. With Baby Mode to track infants or pets, it’s perfect for growing families.
- Precise & Reliable Design: For accuracy and durability, this weight scale is built with advanced sensors, 4 high-sensitivity electrodes, and tempered glass. It measures in 0.2 lb / 0.05 kg increments, auto-calibrates, and supports up to 400 lbs (180 kg).
How to get more repeatable readings
BIA readings can vary with hydration and other conditions. Xiaomi identifies eating or drinking, intense exercise, showering, time of day, clothing, foot cleanliness and moisture, foot placement, illness and physical discomfort as factors that can affect measurements.
- Place the scale on a hard, level floor.
- Measure at roughly the same time each day; Xiaomi recommends morning before eating.
- Use similar light clothing each time, or measure barefoot consistently.
- Avoid measuring immediately after strenuous exercise, a shower, a large meal or substantial water intake.
- Keep the scale surface and soles of your feet clean and dry enough for good contact.
- Stand barefoot with both feet fully on the electrode areas and remain still until measurement finishes.
- Use the same user profile each time.
- Judge changes over several weeks rather than reacting to one unusually high or low estimate.
If body-fat measurement fails, wipe your feet and the scale surface with a moist towel, confirm both feet contact the electrodes, and check that your profile is within Xiaomi’s stated age, height and weight limits. Xiaomi’s online measurement path is Device → select member in the upper-left → Measure. If a family member is assigned the wrong result, manually select the correct profile.
If a reading changes suddenly, first standardize the time, hydration, recent food, exercise, showering, foot condition and profile. A changed reading alone does not show that the hardware is defective.
Best Value
- COMPREHENSIVE FULL-BODY ANALYSIS: The GE smart scale utilizes 8-electrode dual-frequency and segmental BIA technology, segmenting the body into five sections(four limbs and torso) to provide more detailed, consistent body composition estimates for trend tracking
- 50 BODY COMPOSITION METRICS: The GE body fat scale measures not only weight but also BMI, body fat, muscle mass, body water, bone mass, protein, visceral fat, BMR, skeletal muscle, subcutaneous fat, fat-free body weight, metabolic age, etc
- 7 METRICS SHOWN ON DISPLAY: The weight scale with body fat and muscle mass is equipped with an HD LED display, showing 7 key metrics including weight, BMI, body fat, body water, muscle mass, bone mass, and visceral fat. Once the Fit Profile app is downloaded and the initial setup is completed, these metrics can be viewed directly on the scale's display, eliminating the need to open the app each time. It makes health monitoring easy and convenient, great for personal or gym use
- USER-FRIENDLY APP FOR TRACKING AND SHARING: The free app Fit Profile provides detailed charts and saves historical body data so you can track changes in your body composition over days, weeks, months, or years. Easy to set up and works with fitness apps including AppIe Health, for Fitbit, Google Fit, and you can also share your body data changes with your friends and family
- UNLIMITED USERS: The GE body composition scale has a large weighing surface measuring 12.2 in * 13.2 in * 1.3 in (310 * 336 * 33.8 mm). It supports unlimited users, and up to 9 profiles can be created; it instantly recognizes the user when they step on the scale, perfect for families and fitness groups who want to monitor their body data to improve their health
Safety and intended use
Xiaomi says the scale is not a medical device and advises against using its results for diagnosis or treatment. Xiaomi does not recommend it for people with implanted medical devices such as pacemakers or cochlear implants. Pregnant users should use caution. The fact that the scale is not a DEXA device does not make it a substitute for clinical assessment; consult a healthcare professional for medical questions.
Is GeekWills a sensible place to buy it?
GeekWills listed the S400 at $49.90 and “In stock” when observed on August 18, 2026. That is a retailer listing at that time, not an established Xiaomi MSRP or a guarantee of current stock. The page also displays a “2-Year Warranty” signal and estimates Priority Air Mail at 10–15 days and express shipping at 5–10 days. Delivery can depend on destination, carrier, customs and warehouse processing.
The specification conflict deserves attention before the low listed price. Xiaomi’s global page says three AAA batteries, up to 180 days under its test conditions, and Bluetooth with an optional gateway for automatic synchronization. GeekWills lists three AA batteries, about 360 days with once-daily use, and Wi-Fi plus Bluetooth. The available information does not resolve whether that reflects a regional edition or a retailer data-entry error. Ask GeekWills to confirm the exact model number, battery type, native connectivity, app/region support and included packaging in writing.
- Check which country the unit ships from and whether import duties or taxes are due.
- Confirm the return destination, return window and who pays return shipping.
- Ask what the displayed two-year warranty covers, who administers it and whether it is honored in your country.
- Confirm the scale can be set up in your Xiaomi Home region and that the manual and package match the advertised model.
The retailer’s shipping and warranty statements are listing details, not independently established service guarantees. Cross-border returns or warranty claims may be more complicated than buying from a local seller.
Who should buy the S400?
It makes sense if
- You want at-home trend tracking beyond body weight and understand that composition outputs are estimates.
- You are comfortable using Xiaomi Home and do not require a different health platform.
- You want multiple family profiles or app-controlled visitor and infant/pet weighing modes.
- You can confirm the regional model and accept the retailer’s shipping and warranty arrangements.
Look elsewhere if
- You need clinical body-composition measurement or a diagnostic tool.
- You have an implanted electronic medical device, or need advice about use during pregnancy.
- You require confirmed Apple Health, Google Fit, Health Connect, Fitbit, Garmin or Mi Fitness integration.
- You want a domestic warranty and straightforward local returns but cannot verify those terms with the seller.
- Two household members have nearly identical weights and you do not want to choose profiles manually.
Alternatives by ecosystem and need
| Option | Consider it if | What to verify |
|---|---|---|
| Withings Body Smart | You prefer the Withings app and its connected-health ecosystem. | Confirm the integrations and current terms you need; no comparative accuracy claim is established here. |
| Garmin Index S2 | You already use Garmin Connect or Garmin wearables. | Check that its platform fits your needs; no comparative accuracy claim is established here. |
| Basic digital bathroom scale | You need weight tracking, fewer app-account considerations and no body-composition estimates. | For many people, consistent weight readings are sufficient for tracking weight change. |
Verdict
The S400 is best understood as an affordable, feature-rich scale for following at-home trends—not as a DEXA substitute. Its dual-frequency method and broad report may appeal to Xiaomi Home users, but the app lock-in, optional gateway for automatic synchronization and GeekWills’ conflicting specifications are material purchase considerations. Before ordering from GeekWills, get confirmation of the exact regional model, battery, connectivity, app support and warranty terms.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
