Training metrics on Apple Watch Ultra compared to Garmin Fenix

10 min readSep 27, 2022

After happily using Garmin Fenix 6X Pro for two years, I got myself an Apple Watch Ultra. Right after ordering, I started to doubt if it could really replace Fenix for hiking and running. Now having my hands on the watch, I tested that the WorkOutDoors app can almost mitigate the missing offline map.

Today I’ll try to figure out the second major gap in the watch: training metrics.

Ultra lacks some key training metrics like recovery time that have been standard on Garmin for years.

Apple is the king of the hardware

Well-functioning hardware is the pre-requisite for implementing any training metrics. Thus we’ll need to look at the hardware first to set the expectations for the training metrics.

Comparing the following watches in this post due to them being the most interesting to my use case:

Comparing them is tedious — the hardware in these watches is a modern-day miracle: they pack an astonishing number of sensors in a small instrument that is both precise and incredibly durable.

Computing power

Neither Garmin nor Apple speaks much about the computing power in their watches. Thus the specs below are my best guesses based on some teardowns done for these and similar watches — please point out the mistakes here.

  • Ultra, S8: 64-bit dual-core ARM CPU with 3D GPU, running at ~ 1.8GHz. 1GB of RAM. 32GB storage.
  • Fenix 6X: 32-bit single-core ARM CPU, running at up to 150MHz. 16MB of RAM. 32GB storage.
  • Fenix 7X, Epix2: 32-bit dual-core ARM CPU with 2D GPU, running at up to 200MHz. 5MB of RAM. 32GB storage (except in Epix2 non-sapphire edition that has 16GB)

It is safe to say that Apple destroys Garmin when it comes to computing power.

The over-simplified comparison of computing power

With oversimplifying assumptions, I estimate Ultra and S8 to be 24 times faster than Fenix 6X based on the number of CPU cores and clock. Difference could be larger due to 64x memory, efficiency of 64-bit architecture, and different L1/L2 caches. Looks like Fenix 7X and Epix2 might similarly be 3 times faster than 6X, which makes sense for supporting scrolling on the new touch display.


Battery life is an extremely complicated story that I cannot dive deeper into in this post. In addition to what you choose to do with your watch, it is mostly a factor of (a) the size of the battery, (b) the power efficiency of the hardware, and (c) how the software chooses to use the precious mAh. One simplification would be to say that a watch with equal battery capacity should have a potential for equal battery life with another watch if they both choose to spend the battery on the same functions and keep their displays off.

  • Ultra: 542mAh
  • S8: 308mAh
  • Fenix 6X: 420mAh
  • Fenix 7X: Assuming similar to 6X above: ~ 420mAh
  • Epix2: Due to being smaller than 6X watch size, assuming to be in the 300–350mAh range

Interestingly, Ultra has a significantly larger battery than Fenix 6X. But due to Apple choosing to spend the battery differently and Fenix using a very power-efficient transflective LCD, the battery on Fenix lasts 2–5 times what it lasts in Ultra. Both should be sufficient for any sports. During the normal course of life, you need to charge Ultra every 2–3 days and Fenix 6X every 1–2 weeks. I believe that if Apple would choose to implement an “expedition mode” the battery would last weeks on Ultra, but that would also disable everything that elevates it to be a “smarter” watch than Fenix.


Displays are very different on these watches. Epix 2 and Apple Watches use various kinds of OLED displays that are quite similar to each other apart from the exceptional brightness of the Ultra’s display. The transflective LCD on the Fenix series is decades old, but at the same time a brilliant choice for an outdoors watch: the sunlight reflects from the LCD instead of OLED competing with the sun. Garmin watches are round, while Apple devices have a square display. Round may be a more esthetically pleasing shape, but a rectangular display is more practical and simply has more space.

  • Ultra: 410 x 502 LTPO OLED, 2000 nits of brightness, capacitive touch
  • S8: 396 x 484 LTPO OLED, 1000 nits of brightness, capacitive touch
  • Fenix 6X: 280 x 280 Transflective LCD, backlight
  • Fenix 7X: 280 x 280 Transflective LCD, backlight, capacitive touch
  • Epix2: 416 x 416 AMOLED display, 1000 nits of brightness, capacitive touch

There is a clear winner here: Superior brightness in Ultra makes the display the best there has ever been in any wearable.

Sun reflects from Garmin Fenix’s LCD display making it easy to read in bright sunlight

I might also need to note that some Garmin models include a solar panel under the transflective display. While this sounds like a great idea, it does not charge battery life enough to make a difference in normal use.

Accelerometer, gyroscope & compass

All of the compared watches stand on almost equal ground when it comes to measuring which way is up, which way is North, and how fast is your arm swinging. Every watch is good enough.

Apple marketed a fresh generation of super-sensitive accelerometers, but there is no real data available on whether Garmin’s sensors are just as capable.

Global Navigation Satellite Systems (GNSS)

  • Ultra: L1 and L5 GPS, GLONASS, Galileo, QZSS, and BeiDou
  • S8: L1 GPS, GLONASS, Galileo, QZSS, and BeiDou
  • Fenix 6X: GPS, GLONASS, Galileo
  • Fenix 7X, Epix 2: Multifrequency GPS, GLONASS, Galileo. It should be noted that Epix 2 has multifrequency technology only in models with sapphire glass.

The tests show that the multifrequency tech Garmin and L5 GPS on Apple make a real difference in accuracy. I think this simply in terms of two levels of accuracy: Ultra, Fenix 7X and the sapphire edition of Epix 2 are the great ones, the rest of the bunch has sufficient accuracy most of the time, but start guessing between tall buildings or in a forest.

Ultra (yellow) won Fenix 6X (green-blue) in accuracy under tall trees on my evening run.

Pressure sensor

  • S8, Fenix 6X, Fenix 7X, Epix2: Barometric altimeter continuously measures the air pressure to accurately calculate how high up are you.
  • Ultra: In addition to the barometric altimeter, there is a depth gauge that accurately measures water pressure when diving.

Heart rate sensor

  • Ultra, S8: Best in industry accuracy for HR measurement from the wrist.
  • Fenix 6X, Fenix 7X, Epix2: Good enough accuracy most of the time. When added accuracy is needed — for example, to calculate lactate threshold — a separate heart rate monitor is needed.

Benchmarking HR accuracy takes a lot of effort and thus most people just trust the numbers their device shows. The Quantified Scientist has done the best testing I have seen: taking the herculean effort to test the accuracy of various sensors across a wide number of devices — I highly recommend his YouTube channel for diving deeper.

There is a huge difference in HR accuracy between Fenix 7 (R=0.72) and S8 (R=0.98). Data is for cycling.

Blood oxygen sensor

All the compared watches have a blood oxygen saturation sensor that usually takes measurements only while sleeping. After testing a dedicated fingertip sensor, I do not trust the accuracy of either Fenix 6X or Ultra sensors.

Electrocardiogram (ECG) sensor

  • Ultra, S8: One point electrocardiogram sensor takes measures your ECG in a matter of seconds. Fortunately, I do not have need for the sensor.
  • Fenix 6X, Fenix 7X, Epix2: -
Apple Watch can record a single point ECG. You can export result as a PDF and send it to your doctor.

Temperature sensor

  • Ultra, S8: Two thermometers — one against the skin and one not touching the skin. This allows the watch to estimate body temperature against the ambient temperature.
  • Fenix 6X, Fenix 7X, Epix2: One thermometer.

Wireless communications

  • Ultra: Wifi 802.11b/g/n 2.4GHz and 5GHz. Bluetooth 5.3. Cellular LTE+UMTS. NFC.
  • S8: Wifi 802.11b/g/n 2.4GHz and 5GHz. Bluetooth 5.3. Cellular LTE+UMTS on some models. NFC.
  • Fenix 6X, Fenix 7X, Epix2: Bluetooth. Wi-F. Bluetooth. NFC. ANT+.

The significant differences are that: (a) Apple Watch can connect to cellular networks to make calls, send messages, and overall internet connectivity everywhere without a phone, and (b) Garmin can connect to various training sensors using ANT+.

Fenix 6X talks to my mountain bike over ANT+ to measure power and cadence.

Speaker & microphone

  • Ultra: Three-microphone array with beamforming and wind noise mitigation. Dual speakers. So loud that you can use the speakers as an emergency siren that can be heard 600 feet away.
  • S8: Microphone. Speaker.
  • Fenix 6X, Fenix 7X, Epix2: Makes a beep beep beep to wake you up.


  • Ultra: Crown that rotates in two directions and can be pressed, with two other buttons. This makes it a total of 5 buttons in my books.
  • S8: Crown that rotates in two directions and can be pressed, with one other button. This makes it a total of 4buttons in my books.
  • Fenix 6X, Fenix 7X, Epix2: 5 buttons


  • Ultra, S8: Taptic engine generates various haptics to augment the use.
  • Fenix 6X, Fenix 7X, Epix2: Simple vibration motor


  • Ultra, S8, Epix2, Fenix 6X: Can turn the screen on and use it to illuminate surroundings. While this is vastly better than nothing, it is a poor excuse for a flashlight. It needs to be mentioned that Ultra stands above others with its 2000 nits display which is actually quite usable as a flashlight.
  • Fenix 7X: A dedicated white and red LEDs for use as a flashlight. While they are not a replacement for a real flashlight, they are always with you and are better than the competition. You can even use them as strobe lights while running: a red flash when your hand waves back and while flash on the front. How cool is that?
Epix 2 only lights up a small portion of its 1000 nits display, while Ultra blasts every pixel at 2000 nits (a detailed Epix 2 — Ultra comparison by Chase the Summit)

Durability and build quality

  • Ultra: Titanium case. Sapphire crystal, MIL-STD 810H, IP6X dust resistant, 100m water resistant, EN13319 dive certification (to 40 meters).
  • S8: Aluminium or stainless steel case depending on the model. Ion-X glass display on aluminum cases; sapphire crystal on stainless steel. IP6X dust resistant. 50m water resistant, suitable for swimming.
  • Fenix 6X: Fiber-reinforced polymer case with a steel bezel. Gorilla Glass or sapphire crystal. 100m water resistant.
  • Fenix 7X: Fiber-reinforced polymer case with a titanium bezel. Sapphire crystal. 100m water resistant.
  • Epix2: Fiber-reinforced polymer case with a steel or titanium bezel. Gorilla Glass or sapphire crystal. 100m water resistant.

Garmin remains the king of training metrics

Apple and Garmin have very different approaches to training metrics. Apple provides a platform many apps can build on. Garmin is a well-thought-out integrated monolith that just works. I love Garmin’s integrated approach.

Fenix is a tool that just works. Every metric is where it should be, helping you improve.

Most fitness metrics are not dependent on the watch model. I’ll list below the metrics I find relevant and note which work on Apple watch (Ultra and S8 specifically) and which on Garmin Fenix 6/7 and Epix.

Recording an activity

HR, duration, steps, calories, track … all the basics: ✅ Garmin, ✅ Apple

HR zones: ✅ Garmin, ✅ Apple (zones shared between different sports)

Structured workouts: ✅ Garmin, ✅ Apple

Automatically detect reps in strength training: ✅ Garmin (not very accurate, but you can easily adjust them after each set), ❌ Apple.

Map and navigation during activity: ✅ Garmin, ❌ Apple, ✅ Apple with WorkOutDoors app

Vertical oscillation, Stride length, and Ground contact time: ❌ Garmin, ✅ Garmin with HR-Pro belt, ✅ Apple

Running power: ❌ Garmin (grade adjusted pace guidance can be used instead of this), ✅ Apple
Update: A week or so after this post Garmin released a beta version of their watch firmware that adds running power to Garmin watches.

Dynamic grade-adjusted pace guidance: ✅ Garmin, ❌ Apple (running power can be used instead of this)

Cycling power and cadence: ❌ Apple, ❌ Garmin, ✅ Garmin with external sensors connected over ANT+

On-screen workout instruction animations: ❌ Apple, ✅ Garmin

Garmin is the clear winner for recording activities. The Apple Watch ecosystem has dozens of apps for recording various activities. They likely fill most of the gaps, but you need to spend time searching and testing for apps to find something that works for you.

Overall fitness metrics

VO2max: ✅ Garmin (for each sport separately), ✅ Apple

Lactate threshold: ❌ Garmin, ✅ Garmin with HR-Pro belt, ❌ Apple

Race time predictor (5K, 10K, Half, Marathon): ✅ Garmin, ❌ Apple

Heart Rate Variability: ✅ Garmin, ✅ Apple

Acute training load (guiding amount and intensity): ✅ Garmin, ❌ Apple

Recovery: ✅ Garmin, ❌ Apple

Heat acclimation: ✅ Garmin, ❌ Apple

Training plans and calendar: ✅ Garmin, ❌ Apple, ✅ Apple with any of the running coaching apps.

Body battery (overall energy level estimation): ✅ Garmin, ❌ Apple

Sleep amount and stages: ✅ Garmin (with questionable accuracy for sleep stage tracking), ✅ Apple

Which one will I keep?

I am still somewhat on the fence, but will likely keep Apple Watch Ultra due to it being a superior device. What pulls me to Garmin Fenix is the excellent integrated fitness tracking experience and metrics that help me improve.

Almost sure that this will be on my wrist for the next two years.

Ask anything or help correct any mistakes in the comments. App suggestions are highly appreciated as well.

Note: I have purchased both watches myself and have not been paid to promote either. This post contains Amazon affiliate links to the products mentioned. Purchases made through them will help support this site at no cost to you.




Enterpreuner. Geek. Open Source. SF Bay Area. Finn.