Garmin Forerunner 265 Review: Four Months of Marathon Training Data

The Garmin Forerunner 265 ($449) is the best training watch under $500 for marathoners — its Daily Suggested Workouts aligned with our coaching plan 81% of days over an 18-week marathon build, and the AMOLED display is the clearest we've tested in direct sunlight.

Why we spent 18 weeks with one watch and nothing else

Most gear reviews run a product for two weeks and call it a test. We strapped the Forerunner 265 to one editor's wrist on the first day of an 18-week marathon plan and didn't take it off except to charge. 520 training miles. 126 runs. One race. The goal: understand not just what the watch measures, but whether its recommendations change how you train — and whether those changes make you faster or healthier. For comparison against its main competitor in this price tier, see our [Garmin vs Coros head-to-head](/garmin-vs-coros-running-watch).

What the Garmin Forerunner 265 actually gets right

The AMOLED display is the biggest visible upgrade over the Forerunner 255. Readable at noon in August without shade, unlike the MIP display on older models. The Training Readiness score — combining HRV Status, sleep score, and training load — was accurate enough that we began skipping our manual morning HRV app check after week four. Battery: we averaged 22 hours of actual GPS use per charge cycle, consistent with Garmin's 24-hour claim. Charging from 10% to 100% takes 65 minutes via USB-C.

What the Forerunner 265 gets wrong

The wrist-based HR sensor underreads during interval sessions by an average of 8 bpm compared to our Garmin HRM-Pro chest strap — significant enough to affect zone targeting on short hard efforts. Garmin's Connect app remains cluttered; finding the Training Readiness score history requires four taps. Weight at 47g is acceptable but noticeable compared to Coros Pace 3 at 30g — runners who are sensitive to wrist weight during tempo runs will feel the difference.

How we tested the Forerunner 265

Step 1: Daily readiness accuracy

We logged perceived readiness each morning (1–10 scale) before checking the watch's Training Readiness score. Over 126 mornings, our subjective score and the watch score aligned within 2 points on 81% of days. Misalignments clustered around travel days and unusual stress events — predictable gaps in any biometric algorithm.

Step 2: HR accuracy at varying intensities

We ran 20 structured interval sessions comparing wrist HR to Garmin HRM-Pro chest strap. At easy pace (under 135 bpm): ±3 bpm average error. At tempo (155–165 bpm): ±5 bpm. At VO2 max intervals (175+ bpm): ±8 bpm. For easy and long runs, wrist HR is adequate. For precise interval targeting, pair with a chest strap.

Step 3: Race day performance

We ran a target marathon wearing the watch. GPS tracked 26.24 miles on a certified 26.22-mile course (0.08% error). Pace data was stable and accurate throughout. The Race Predictor function estimated our finish time within 4 minutes of actual performance — a useful sanity check for goal-setting.

Is the Garmin Forerunner 265 worth it over the 255?

Yes, primarily for the AMOLED display and improved Training Readiness algorithm. The display difference alone is worth $80 if you train in variable light conditions. If you primarily train indoors or at dawn/dusk in softer light, the Forerunner 255 at $349 covers the core training metrics with a less readable display.

Does the Garmin Forerunner 265 work with a phone?

Yes — Bluetooth sync to Garmin Connect app on iOS and Android. Notifications (calls, texts, calendar) display on the watch face. Music controls work with Spotify, Apple Music, and downloaded content. You don't need a phone for GPS — the watch has its own GPS receiver. Phone pairing adds notifications and faster weather updates.

How do I extend Garmin Forerunner 265 battery life?

Three settings extend battery meaningfully: switch from All Systems GPS to GPS-only mode (+4 hours), disable wrist HR during sleep tracking (+1.5 hours), and reduce display brightness from auto to 30% (+2 hours). Combined: extends GPS runtime from 24 to approximately 31 hours. Enable these settings for races beyond marathon distance where charging isn't available.