How to Change Weight Units on Apple Watch, Garmin & MyFitnessPal

If you know your weight in stone but your wearable keeps insisting on kilograms — or the reverse — you are not alone. This guide walks through the exact steps to align all three to whichever unit you prefer.

Introduction

If you know your weight in stone but your wearable keeps insisting on kilograms — or the reverse — you are not alone. Apple Health, Garmin Connect and MyFitnessPal each store weight data in metric by default, yet all three offer full support for stones and pounds. The catch is that the setting is buried differently in each platform, and changing it in one place does not always cascade to the others. This guide walks through the exact steps to align all three to whichever unit you prefer, so your weight data is consistent across every app and device you use.

UK adults are unusual in the global fitness tech landscape: we think in stone for personal weight, in kilograms at the gym, and sometimes in pounds when reading American content. That three-way mental juggle is precisely what these settings are designed to eliminate — if you know where to find them. You can convert your weight between kg and stone instantly to check your figures as you go.

⌚ Apple Watch & Apple Health

Apple Watch does not have its own weight unit setting. All unit changes are made through the iPhone Health app and then sync automatically to the watch. Attempting to change units on the watch itself has no effect.

Step	Action	Detail
1	Open Health app on iPhone	Tap the Health app icon — not the Fitness app. They are separate.
2	Tap Browse (bottom right)	This opens the full list of health categories.
3	Select Body Measurements	Scroll down to find it, or use the search bar at the top.
4	Tap Weight	Your current weight entry will appear.
5	Scroll to Unit	At the bottom of the Weight screen, tap Unit.
6	Select your unit	Choose from kg, lbs, or stone. Changes apply immediately.
7	Sync to Apple Watch	Open the Watch app on iPhone → My Watch → Health → Health Details — confirm the unit is reflected.

Important: If your Apple Watch still shows the old unit after following these steps, unpairing and re-pairing the watch with your iPhone will force a full settings sync. This is particularly common after moving between countries with different regional defaults.

★ Common Gotcha — Apple Watch

You cannot change weight units directly on the Apple Watch itself. Every forum thread that suggests otherwise is referring to an older watchOS version. As of watchOS 10 and later, all body measurement unit changes must be made in the iPhone's Health app. The watch will update on next sync.

🛰️ Garmin Connect

Garmin separates watch settings from app settings. Changes made in the Garmin Connect app do not automatically update what your Garmin watch displays, and vice versa. You need to configure both independently if you want everything to match.

Steps: Garmin Watch (On-Device)

Step	Action	Detail
1	Hold the Up/Menu button	Hold until the settings menu appears on screen.
2	Scroll to System	Use the Down button to navigate.
3	Select Format	On some models this is labelled System > Units directly.
4	Select Units	Opens the full units sub-menu.
5	Select Weight	From here, choose kg, lbs, or stone. Changes save automatically.

Steps: Garmin Connect App (iOS & Android)

Step	Action	Detail
1	Open Garmin Connect	Tap the app and sign in.
2	Tap the profile icon (top left)	This opens your user profile.
3	Tap Settings	Then tap User Settings.
4	Select Units of Measure	Three options: Metric, Statute, or Statute UK.
5	Choose Statute UK	Enables stone and pounds as weight options.
6	Open weight data	Navigate to Health Stats > Weight in the app.
7	Tap the three dots (top right)	Select preferred display — this final step activates stone display and is easy to miss.

★ Garmin's Hidden Step

Setting Garmin Connect to 'Statute UK' is not enough on its own. You must then open your weight data and tap the three dots in the top-right corner to switch the display to stone and pounds. Many users set the region correctly but miss this second step — the app continues to show pounds until you action it.

🍽️ MyFitnessPal

MyFitnessPal offers stones and pounds as a full unit option alongside kilograms and pounds. The setting lives in your profile, and any change made in the app automatically updates the web version and vice versa. Past weight entries are retroactively converted when you switch units.

Steps: MyFitnessPal App (iOS & Android)

Step	Action	Detail
1	Open MyFitnessPal	Tap the app and log in.
2	Tap More (bottom right)	Icon shows three dots or lines depending on OS.
3	Tap Settings	Then navigate to My Account.
4	Tap Edit Profile	On some versions, tap your profile photo first.
5	Tap Units	Opens the full unit selection screen.
6	Tap Weight	Select from kg, lbs, or stones/lbs.
7	Save / Confirm	Tap OK or the checkmark. Data converts automatically.

Steps: MyFitnessPal Web

Step	Action	Detail
1	Go to myfitnesspal.com	Log in to your account.
2	Click My Home	In the top navigation bar.
3	Click Settings	From the dropdown menu.
4	Click Change Units	In the left-hand sidebar.
5	Change Weight unit	Select preferred unit from the dropdown.
6	Click Save Changes	Changes sync to the mobile app automatically.

Platform Comparison at a Glance

Platform	Where to Change	Units Available	Notes
Apple Health	Health app → Body Measurements → Weight	kg, lbs, stone	Watch syncs from iPhone only
Garmin Connect	Profile → Settings → Units of Measure → Statute UK	Metric / Statute / UK	Must also tap 3 dots in weight view
Garmin Watch	Menu → System → Format → Units → Weight	kg, lbs, stone	Independent of app — set separately
MyFitnessPal	More → Settings → My Account → Units → Weight	kg, lbs, stone/lbs	Historical entries auto-convert

Once your units are aligned, you can check your BMI accurately across all platforms.

Why These Settings Exist Separately

Each platform stores weight data in a single master unit internally — almost always kilograms, which is the SI (International System of Units) standard used in science and medicine globally. The unit you choose in the settings interface is a display preference only, not a change to how the data is actually stored. This is why switching back and forth does not corrupt your historical data, and why your records survive the conversion intact.

The disconnect between watch and app settings in Garmin's ecosystem exists because the watch operates as a standalone device that only syncs selected data rather than mirroring all account preferences. Apple took a different approach by tying the watch display entirely to the iPhone's Health app, which is why you cannot make the change on the watch itself.

Doctor's Note — Dr Muhammad Usman, MBBS

"In clinical practice, patient records in the UK typically use kilograms for drug dosing, anaesthetic calculations and BMI screening, while many patients report their weight in stone when asked. This mismatch is clinically relevant. Configuring your fitness devices to show the unit you are most fluent in reduces the mental conversion step and helps you engage more accurately with your own health data."

Frequently Asked Questions

How do I change weight to kg on Apple Watch?

You cannot change the unit directly on the Apple Watch. Open the Health app on your paired iPhone, tap Browse, then Body Measurements, then Weight, then Unit and select kg. The watch reflects the change on next sync.

How do I change Garmin weight units to stone?

In Garmin Connect, go to Profile > Settings > User Settings > Units of Measure and choose Statute UK. Then open your weight data and tap the three dots (top right) to switch to stone display.

How do I change MyFitnessPal from stone to kg?

In the app: More > Settings > My Account > Edit Profile > Units > Weight > select kg. On the website: My Home > Settings > Change Units.

Will changing units in MyFitnessPal affect old entries?

Yes. MyFitnessPal automatically converts all historical weight entries to the new unit. No data is lost.

Why does my Apple Watch show a different unit to my iPhone?

Update the unit in iPhone Health app and unpair/re-pair the watch to force a full settings sync.

Changing Units on Your Wearables: A Step-by-Step Guide