Apple Watch and Galaxy Watch: what data they share and what FitMesh can use

Apple Watch and Galaxy Watch both record heart rate, sleep, steps and workouts, and both pass them to the phone's health store: Apple Health on iPhone, Health Connect on Android. Part of what the watch shows on its screen never leaves its own app, such as brand scores, and some measurements depend on the model and the country. FitMesh Sync reads what Apple Health or Health Connect holds, with your permission.

What each watch shares with the phone

The table summarizes what the sources consulted document. It describes data stores, not FitMesh screens: the last column points to the compatibility selector, where each combination has a status and its limits.

Measurements that depend on model and country

• •ECG. Apple Watch Series 4 or later and Ultra, where the ECG app is available (Apple Support); not on Apple Watch SE. On Galaxy Watch it needs the Samsung Health Monitor app, a Galaxy phone with Android 12 or later and a country where the app has been released (Samsung Support). No ECG recording appears in Samsung's list of data synced to Health Connect.
• •Blood pressure (Galaxy Watch). According to Samsung it requires an initial calibration and then one every 28 days with a separate upper-arm cuff, a Galaxy phone with Android 12 or later and a country where the feature has been released (Samsung Support). Samsung's developer table lists blood pressure among the data that can reach Health Connect and says the scope depends on the Samsung Health version (Samsung Developer).
• •Body composition, BIA (Galaxy Watch). Available from the Galaxy Watch4 series onward. Samsung documents body fat, weight and basal metabolic rate reaching Health Connect (Samsung Developer); for other values the sources consulted say nothing.
• •Blood oxygen (Apple Watch). By default it is available only in certain countries and regions: check Apple's availability page (Apple Support).

Why HRV from the two watches is not comparable

Heart rate variability (HRV) is the variation in time between one heartbeat and the next. Two common calculations give it in milliseconds, which makes values from different watches look interchangeable: SDNN and RMSSD.

• •SDNN measures how widely the intervals between beats are spread overall. Apple Health stores Apple Watch readings as SDNN (Apple HealthKit documentation).
• •RMSSD measures the differences between consecutive intervals and mostly reflects short-term changes linked to rest and recovery. Health Connect defines a record type for it (Android Developers), but it only stores what an app calculates and writes there.
• •Samsung's list of data synced from Samsung Health to Health Connect has no HRV entry, so an HRV value shown in Samsung Health should not be assumed to appear in Health Connect.

No fixed factor converts SDNN into RMSSD. Apple has not published the formulas behind Recovery HRV and Overall HRV, so the names do not tell you which calculation they use (Apple Newsroom, September 9, 2026). Compare HRV only with readings from the same watch and the same method. For what the values mean: HRV values explained.

Scores that stay in the brand's app

Apple's Readiness score runs from 0 to 10 and is available on Apple Watch Series 12 and Ultra 4 (Apple Support). Vitals compares overnight measurements with your typical range (Apple Support). Samsung describes its Energy Score as the daily measurement of physical and mental readiness, without stating a value range, and offers read-only access through the Samsung Health Data SDK (Samsung Developer). In the HealthKit documentation and the Health Connect data types consulted, none of these scores has a matching type, so we found no data type through which another app could read them from the phone's health store. FitMesh does not read them.

What FitMesh can use

FitMesh Sync reads, with your permission, the data that Apple Health (iPhone) or Health Connect (Android) already holds. For Apple Watch and Galaxy Watch, the compatibility selector marks steps, heart rate and sleep with stages as documented routes, workouts as conditional, and HRV, blood oxygen and temperature as not verified. Where the selector says not verified, do not expect FitMesh to show that value. The selector is available in Italian and English.

For the details of each route: how Health Connect works on Android, the new Apple Health on iPhone, and Health Connect on Galaxy Watch Ultra2 and Watch9.