Garmin Forerunner 265

What Garmin publishes

The battery table below is from Garmin's own owner's manual, with the satellite mode named on every row — because the gap between the flattering figure and the accuracy figure is six hours, which is most of a long run.

Note the oddity: the smaller 265S states longer battery than the 46mm 265 in every mode. That is a screen-size effect rather than a bigger cell, and it is a rare case where the small watch is not the compromise. The manual also states 5 ATM and up to 8 GB of media storage for both.

The study, in full

In 2025 a research group published a comparison of smartwatch threshold estimates against fingertip blood lactate — the laboratory standard — in 100 recreational runners. Three watches were tested. The Forerunner 265 was one of them, worn by 23 of the runners, and this is what happened:

• Threshold pace: 25.78% mean error, and it overestimated. The watch told runners they could sustain a faster pace than the laboratory said they could. Of the three watches, it was the least accurate on pace.
• Threshold heart rate: much better, inside the 5.95-7.15% band the three watches shared, which works out to roughly 9-11 bpm. Still, no device met statistical equivalence with the laboratory.
• Test success rate: 65.2%. More than a third of attempts did not return a usable result at all.

Two caveats the authors publish, which we will not bury. The device samples were unequal — 100 runners wore the Huawei, 23 the Garmin and 17 the COROS — and the Garmin protocol required an ECG chest strap while the other two devices used wrist sensing, so the comparison between brands is not perfectly like for like. The reference standard itself, a treadmill graded exercise test with fingertip blood lactate, is the strongest available.

We rank this watch higher on evidence than most of its rivals despite that result, and the reasoning is worth stating plainly: a measured device with a known flaw is a better-understood purchase than an unmeasured device with a marketing claim. The rivals are not better — they are untested. The rubric is published if you want to check that reasoning against the numbers.

What it is like as a watch

Excellent, and unremarkable in the way good tools are. The AMOLED is bright, the multi-band receiver is the specification that actually improves tracks in cities and under trees, and Garmin's training platform is the most complete in the category. Two case sizes cover most wrists. There are no maps — routes appear as a breadcrumb line with off-course alerts — and no speaker or microphone.

At $25.00 per stated hour in the accuracy mode, it is mid-pack for the site: better than the fēnix tier, well behind the COROS PACE 4.

How to use it well

Set your zones from a real test — a field test you repeat, or a laboratory test if you have access to one — rather than from the watch's own threshold estimate. Use the estimate as a trend line, which is what a 25.78% pace error still allows: it will tell you the direction you are moving even when the absolute number is wrong.

And pair a strap for intervals. The published placement evidence is unambiguous that wrist-worn optical sensors lose agreement during rapid intensity changes, whatever the brand — which is the entire subject of our wrist versus chest strap page.

Against its own siblings

The 265 sits between two Forerunners it is worth measuring against directly, using Garmin's own figures in the same modes:

• Versus the Forerunner 570. Identical 14 stated hours in All + Multi-Band and identical 8 GB of media storage. The 570 adds a speaker, a microphone, a 42mm option with the full feature set and two extra hours of recording with music. The 265 states two more GPS-only hours and two more smartwatch days. The full comparison is here.
• Versus the Forerunner 965. Not close: 19 stated multi-band hours against 14, 32 GB of media against 8, and built-in maps the 265 does not have at any setting.

The reason to buy the 265 anyway is that it does the mid-range job at a mid-range price with a multi-band receiver — and that it is the one watch here whose behavior a research group has actually checked.