Scale Relay
Mi Body Composition Scale 2 to Garmin Connect on iPhone
The Mi Body Composition Scale 2 is the cheapest body-composition scale most Garmin owners will ever buy, and Garmin Connect cannot see it. This guide shows how Scale Relay reads the scale over Bluetooth and sends weight, body fat, muscle, water and bone mass to Garmin Connect from your iPhone, with no Xiaomi account and no extra hardware.
What you need
- A Mi Body Composition Scale 2 (Xiaomi model XMTZC05HM, the white 30 × 30 cm scale sold since 2019). The weight-only Mi Smart Scale 2 shows weight but has no impedance electrodes, so it cannot produce body composition.
- An iPhone with iOS 17 or later and Bluetooth switched on.
- A Garmin Connect account. Two-factor authentication is fine.
- Scale Relay from the App Store. The first two Garmin uploads are free.
You do not need Zepp Life, Mi Fit, Xiaomi Home, a Xiaomi account, a Raspberry Pi or a computer. If you are weighing up other approaches first, see every way to get a Xiaomi scale into Garmin Connect.
Not a Xiaomi scale? If your scale's app saves weigh-ins to Apple Health (Withings, Renpho, Eufy, Etekcity, Zepp Life and most others), Scale Relay can relay them to Garmin Connect too: weight, plus body fat and BMI when the app provides them. See the Apple Health guide.
How the Scale 2 talks to your iPhone
The Mi Body Composition Scale 2 does not need to be paired. Every time you step on it, it broadcasts the measurement as a short Bluetooth Low Energy advertisement: your weight, and once the electrodes have a stable reading, your body impedance. Scale Relay listens for these broadcasts while it is open, recognises the scale automatically and turns weight plus impedance into body composition using your height, age and sex. Nothing leaves the phone until you tap send.
This is why setup takes a minute rather than an evening. There is no Bluetooth pairing dialog, no MAC address to type in and no key to extract.
Step by step
-
Install Scale Relay and allow Bluetooth
Download Scale Relay from the App Store, open it and allow Bluetooth access when iOS asks. Scale Relay only uses Bluetooth to listen for the scale; it does not connect to anything else.
-
Enter your profile
Open Settings and enter your sex, height and age. The scale only measures weight and impedance; body fat, muscle mass, water and bone mass are calculated from those two numbers and your profile, the same way the Xiaomi app does it. A wrong height is the most common reason for a body-fat number that looks off.
-
Weigh yourself with the app open
Go back to the main screen, which says Step on scale, and step on the scale barefoot. You will see your weight update live while it settles. Stand still until the number stops changing and the scale has had a second or two to measure impedance, then step off. Socks or wet feet block the impedance reading and you will get weight only.
-
Review the measurement
Scale Relay shows weight, BMI, body fat, body water, muscle mass, bone mass and BMR. If something looks wrong, step on again; only the measurement you send goes to Garmin.
-
Sign in to Garmin Connect (first time only)
Tap send. The first time, Scale Relay asks for your Garmin email and password and, if your account uses two-factor authentication, for the verification code from your email or authenticator app. The sign-in is stored in the iOS Keychain, so you do this once.
-
Send to Garmin and check
Scale Relay uploads the measurement and confirms when Garmin Connect has accepted it. Open Garmin Connect, go to Health Stats › Weight, and the entry appears with the body-composition values. Your first two uploads are free; after that, unlimited uploads are a one-time $14.99 purchase.
Ready to try it? Get Scale Relay on the App Store; the first two Garmin syncs are free.
What is transferred to Garmin Connect
| Metric | Source | Sent to Garmin Connect |
|---|---|---|
| Weight | Measured by the scale | Yes |
| BMI | Calculated from weight and height | Yes |
| Body fat % | Calculated from impedance | Yes |
| Body water % | Calculated from impedance | Yes |
| Muscle mass | Calculated from impedance | Yes |
| Bone mass | Calculated from impedance | Yes |
| Visceral fat rating | Calculated from impedance | Yes |
| Metabolic age and physique rating | Calculated from impedance | Yes |
| BMR | Calculated from impedance | Shown in the app |
Garmin Connect treats the upload like a measurement from its own Index scale, so the values show up in the weight graph, the body-composition cards and in the daily summary. Measurements are timestamped with the time you weighed yourself.
About the numbers. Body composition from any consumer scale is an estimate from electrical impedance. Scale Relay uses the same kind of formulas as the Xiaomi app, so day-to-day trends are meaningful; a single reading is not a medical measurement.
Troubleshooting
The scale is not detected
- Check that Bluetooth is on and that Scale Relay has Bluetooth permission in iOS Settings › Privacy & Security › Bluetooth.
- The scale only broadcasts while it is awake. Step on it, or tap it with your foot, with Scale Relay already open.
- Stay within a few metres. Bathroom walls and a phone left in another room are enough to lose the broadcast.
- If another app such as Zepp Life is open and holding a connection to the scale, close it and try again.
Weight arrives but body composition is missing
- Measure barefoot with dry feet, and stand still until the scale has finished. Impedance is measured a moment after the weight stabilises.
- Make sure your height, age and sex are filled in under Settings.
- Very high or very low impedance readings are rejected by the scale itself; try again after drying your feet.
Garmin sign-in fails
- Use the email and password of your Garmin account, not a Garmin Connect username.
- If your account uses two-factor authentication, enter the code Scale Relay asks for; codes expire quickly, so request a fresh one if it is rejected.
- After several failed attempts Garmin temporarily blocks sign-ins for a while. Wait a few minutes before trying again.
- In mainland China: Scale Relay signs in to connect.garmin.com only; Garmin China (garmin.cn) accounts are separate and not supported.
The measurement is not in Garmin Connect
- Scale Relay confirms every accepted upload. If the upload failed, the measurement stays queued in the app: open Scale Relay and tap Retry. Nothing is sent in the background.
- Pull to refresh in Garmin Connect, and check the date of the entry: uploads use the time you weighed yourself.
More than one person uses the scale
Scale Relay currently keeps one profile. Change the height, age and sex in Settings before another person weighs in, or use it for the one Garmin account that needs the data.
Frequently asked questions
Do I need the Zepp Life or Xiaomi Home app?
No. The scale broadcasts each measurement and Scale Relay reads it directly. You do not need a Xiaomi account, and you can keep using Zepp Life alongside Scale Relay if you like its history view.
Does Scale Relay work in the background?
No. Open the app before you step on the scale; it listens while it is on screen. A failed upload stays queued until you open the app and tap Retry.
Does it support Garmin two-factor authentication?
Yes. When Garmin asks for a verification code, Scale Relay prompts you for the code from your email or authenticator app.
How much does it cost?
Free to download, first two successful Garmin uploads free, then a one-time $14.99 purchase for unlimited uploads. No subscription.
Does Scale Relay write to Apple Health?
No. It reads the scale, calculates body composition on your iPhone and uploads to Garmin Connect only when you choose to.
Is my data private?
Measurements are processed on the phone and are not stored on any Scale Relay server. The app has no analytics, advertising or tracking frameworks. Garmin credentials are stored in the iOS Keychain and used only for the upload you request.
Get Scale Relay
Read your Mi Body Composition Scale 2 and send the result to Garmin Connect. Two Garmin uploads are free, then a one-time $14.99 purchase.
Download on the App StoreIndependent app. Not affiliated with Garmin or Xiaomi.
