Endurometry
The Forerunner 265 is Garmin’s AMOLED mid-range running watch. It has the smallest battery in this comparison, and that is the trade-off for the brightest screen — but 20 hours of GPS is still far more than any road marathon needs.
All figures below are Garmin’s published numbers for the 46 mm model. The smaller 265S lasts longer per charge (24 h GPS, 15 days smartwatch) because it has a smaller display to drive.
Battery life compared
| Mode | Forerunner 265 This watch | Forerunner 965 | fēnix 8 | Venu 3 |
|---|---|---|---|---|
| Smartwatch mode | 13 days | 23 days | 16 days always-on 7 days | 14 days always-on 5 days |
| Battery saver mode | — | — | 23 days | 26 days |
| GPS-only | 20 hours | 31 hours | 47 hours always-on 37 hours | 26 hours |
| SatIQ / AutoSelect | 16 hours | 22 hours | 38 hours always-on 30 hours | — |
| All systems + multi-band | 14 hours | 19 hours | 35 hours always-on 28 hours | — |
| GPS + music | 7 hours | 10.5 hours | 10 hours | 11 hours |
| Max battery GPS | — | 34 hours | 81 hours | — |
| Expedition GPS | — | — | 17 days | — |
Official Garmin figures, gesture-activated display unless noted. Real battery life depends on the features you have enabled — GPS mode, music, Pulse Ox and always-on display all cost hours.
“—” means Garmin does not publish that figure separately for this watch. We leave it blank rather than estimate.
Specs
| Size | 46 mm |
| Display | 1.3″ AMOLED |
| Storage | 8 GB |
| Positioning | GPS / GLONASS / Galileo · SatIQ · 多频 |
| Released | 2023 |
Is it the right watch for your running?
The AMOLED mid-range pick. It has the shortest smartwatch battery here, but 20 hours of GPS-only will get you through any road marathon with hours to spare, and you get multi-band GPS and training readiness in a much lighter watch than the 965.
Buy it if you want the bright screen and modern training metrics without paying flagship money, and your longest race is a road marathon. Look elsewhere if you run long trail ultras or want maps on your wrist.
Related Tools
Training Pace Calculator (VDOT Zones)
Get your VDOT from a recent race and see easy, marathon, threshold, interval and repetition pace zones plus heart-rate zones.
Race Time Predictor
Predict your finish time at any distance using the Riegel power law and the Daniels–Gilbert VO2max model.
Pace Chart Generator
Enter a goal finish time and get a pace chart in both min/km and min/mile, a speed-to-pace conversion table, your tempo pace and a printable wristband.
Frequently Asked Questions
How long does the Forerunner 265 battery last in GPS mode?
Up to 20 hours in GPS-only mode with wrist-based heart rate, according to Garmin’s specifications for the 46 mm model.
Does the always-on display change battery life?
Yes, substantially. Garmin lists about 13 days with the gesture-activated display and about 5 days with always-on enabled.
Is 20 hours of GPS enough for an ultra?
For a road marathon, comfortably. For a 100 km race or a long mountain ultra, look at the fēnix 8 — 47 hours of GPS and 81 hours in max-battery GPS mode.
Related Tools
Running Pace Calculator
Enter distance and finish time to get your pace per km and mile, average speed and per-kilometre splits.
Running Pace Converter
Convert between min/km, min/mi, km/h and mph, and see the implied finish time for 5K, 10K, half marathon and marathon.
KPH to MPH Converter (km/h to mph)
Convert kph to mph instantly: mph = km/h × 0.621371, so 100 km/h = 62.14 mph. Free km/h to miles per hour chart for road and running speeds, plus mph to km/h.
Race Time Predictor
Predict your finish time at any distance using the Riegel power law and the Daniels–Gilbert VO2max model.
Training Pace Calculator (VDOT Zones)
Get your VDOT from a recent race and see easy, marathon, threshold, interval and repetition pace zones plus heart-rate zones.
Age Grading Calculator
Convert a finish time to an approximate open-class (20–29) equivalent using Endurometry age factors — not official WMA tables.
Want a new tool or fix?
Tell us which calculator, pace chart or fix would help — we build what runners ask for. Replies usually come back in 1–2 days.