Garmin Forerunner 965 vs Fenix 8: Same PPG Sensor, Different Watches
The Garmin Forerunner 965 and Fenix 8 share the same Elevate v5 PPG sensor and Firstbeat Analytics engine, but differ significantly in build quality, battery life, and price. For runners and triathletes choosing between these two premium Garmin watches, the PPG hardware is identical -- so the decision comes down to durability, features, and value rather than sensor accuracy differences.
Specifications Comparison
| Specification | Garmin Forerunner 965 | Garmin Fenix 8 |
|---|---|---|
| PPG Sensor | Elevate v5: green, red, IR LEDs, 4 photodiodes | Elevate v5: green, red, IR LEDs, 4 photodiodes |
| Sampling Rate | 25 Hz continuous, 100 Hz workout mode | 25 Hz continuous, 100 Hz workout mode |
| LED Wavelengths | Green 520 nm, Red 660 nm, IR 940 nm | Green 520 nm, Red 660 nm, IR 940 nm |
| Battery Life | 23 days smartwatch, 31 hours GPS | 28 days smartwatch (solar), 48 hours GPS |
| Price | $499 | $999 (AMOLED), $1,099–$1,299 (Solar/Sapphire) |
| Weight | 53 g | 53–97 g (size/material dependent) |
| Water Resistance | 5 ATM (50 m) | 10 ATM (100 m) |
| SpO2 | Yes, Pulse Ox (resting) | Yes, Pulse Ox (resting) |
| Display | 1.4" AMOLED, 454 x 454 | 1.4" AMOLED or 1.4" MIP + Solar |
| Case Material | Fiber-reinforced polymer | Titanium, stainless steel, or polymer |
Pros & Cons
Garmin Forerunner 965
Pros
- + Same Elevate v5 PPG sensor as Fenix 8 at a lower price point
- + Bright AMOLED display with excellent workout readability
- + Full training analytics suite including Training Readiness and HRV Status
- + Lighter weight optimized for running comfort
Cons
- - Polymer case less durable than Fenix titanium/steel options
- - No solar charging option available
- - Shorter battery life than Fenix 8 (23 days vs 28 days)
Garmin Fenix 8
Pros
- + Premium build with titanium and sapphire glass options
- + Solar charging extends battery up to 28+ days
- + Dive-ready with 10 ATM water resistance
- + Larger storage for maps and music (32 GB)
Cons
- - Significantly higher price ($999-$1,299) for same PPG sensor
- - Heavier weight can be noticeable during fast running
- - Premium materials add cost without improving sensor accuracy
Verdict
Since both watches use the identical Elevate v5 PPG sensor and Firstbeat Analytics engine, heart rate accuracy, HRV tracking, and SpO2 measurement are functionally the same. The Forerunner 965 at $499 offers the best value for runners and triathletes who want top-tier PPG performance without paying for premium build materials. The Fenix 8 justifies its premium for mountaineers, divers, and users who need solar charging for extended backcountry use. From a PPG perspective, save your money and get the Forerunner 965 unless you specifically need the Fenix's durability features.
Frequently Asked Questions
Is the PPG sensor different between Forerunner 965 and Fenix 8?
No. Both use the identical Garmin Elevate v5 sensor with the same LED configuration, photodiode array, sampling rates, and algorithms. Heart rate, HRV, and SpO2 accuracy are the same on both watches. The price difference reflects build quality and features, not sensor capability.
Which Garmin is better for triathlon training?
The Forerunner 965 is purpose-built for triathlon with its lighter weight, AMOLED display, and focused multisport features. The Fenix 8 offers identical training features in a more durable package. For pure triathlon training, the Forerunner 965 provides better value.
Does the Fenix 8's heavier weight affect PPG accuracy?
The heavier Fenix 8 may actually provide marginally better PPG contact pressure during some activities due to its mass, but this effect is minimal. Both watches should be worn snugly 1-2 finger widths above the wrist bone for optimal PPG signal quality.