Best GPS Watch for Marathon Training: Seven Picks for an 18-Week Build

Who this page is for

The best GPS watch for marathon training, for most runners, is the Garmin Forerunner 970. It pairs training readiness and running tolerance (tools for deciding whether today's run should be easy or hard) with preloaded maps for unfamiliar long-run routes and up to 26 hours of GPS-only tracking. If you would rather have more battery in a lighter case, the COROS Pace 4 is rated for up to 31 hours in dual-frequency mode at 40 g.

This page is for runners in a marathon build, or finishing a half and planning the full. If you're still building toward your first 10K, a marathon watch is more than you need: see our best running watches for beginners instead.

What marathon training asks of a watch

A beginner watch has one job: tell you how far you went. In a marathon block the job grows. Here is what the 18 weeks actually ask for, and which specs answer each need.

• Battery for the week, not just the run. Every watch here covers a 20-miler with hours to spare. What varies is how many training days you get between charges once long runs and midweek runs pile up.
• A way to manage the load. Weekly running more than doubles over the plan. Garmin lists training readiness on the 970, 965 and 570, and running tolerance on the 970. COROS lists EvoLab (recovery, fatigue and training load) on the Pace 4. Polar lists Training Load Pro and Recovery Pro, and Suunto lists Suunto Coach on the Race 2.
• Routes you haven't run before. A 20-mile run often means leaving your usual loops. Maps are listed on the Forerunner 970 and 965 (preloaded), the Pace 4 (downloadable), both Suuntos and the Polar. The Forerunner 570 has none.
• Race-day pacing. Suunto lists a Marathon mode with real-time finish prediction on the Run 2. Garmin lists realtime stamina on the 970, and COROS lists a race predictor in EvoLab.
• Music on long runs, if you want it. Garmin rates the 970 for up to 14 hours GPS-only with music and the 570 for up to 9. COROS and the Suunto Run 2 list onboard music storage. The Polar Vantage M3 lists music controls only, for music playing on your phone.

The battery math for a 20-mile long run

Here is the arithmetic, using a 12-minute mile purely to do the math (it is not a target). At that pace the 20-miler is four hours of GPS recording, and a 40-mile peak week is eight hours. Even the shortest GPS-only figure among the dedicated running watches here, the Forerunner 570's up to 18 hours, covers that peak week's running more than twice over before you count smartwatch use.

So battery isn't a pass/fail test at this level. It's about how often you want to charge. Weekly charging suits almost everyone. If you want to charge rarely, the Pace 4 (up to 31 hours dual-frequency, up to 19 days daily use) and Suunto Race 2 (up to 55 hours dual-band, up to 18 days as a smartwatch) lead the list. Watch the mode names, though: every maker lists fewer hours in its multi-band or dual-frequency mode than in its basic mode.

The Garmins, side by side:

And the COROS, Suunto and Polar picks:

Pick by pick, for a marathon build

1. Garmin Forerunner 970: the complete marathon toolkit

Garmin's current flagship Forerunner lists nearly every training tool a marathoner might use: training readiness, running tolerance, realtime stamina, running power, endurance score and hill score. Add preloaded road and trail maps, a built-in speaker and microphone, an LED flashlight for dark early starts, and a sapphire lens. At 56 g it is the heaviest Garmin here, and its GPS-only figure (up to 26 hours) is shorter than the older 965's. For most people training for a marathon, those are fair trades.

2. COROS Pace 4: long battery, light case

COROS rates the Pace 4 for up to 41 hours with all satellite systems on, and up to 31 hours even in all-systems dual-frequency mode. That is the best multi-band figure on this list apart from the much heavier Suunto Race 2. It adds downloadable maps with back-to-start, COROS training plans and EvoLab load tools, and weighs 40 g (32 g on nylon). Its gaps are small: a mineral glass lens rather than sapphire, no contactless payment on the spec list, and daily battery that drops from 19 days to 6 with the display always on.

3. Garmin Forerunner 965: the longest-lasting Garmin

The previous-generation flagship is still sold by Garmin and lists the longest battery of any Garmin here: up to 31 hours GPS-only and up to 23 days as a smartwatch. You get preloaded maps, 32 GB of storage, endurance score and hill score. You miss the 970's running tolerance, flashlight and speaker, and the case is the largest Garmin here at 47.2 mm.

4. Garmin Forerunner 570: the one for smaller wrists

The 570 comes in 42 mm (42 g) and 47 mm (50 g), and Garmin lists the smaller case for wrists from 115 to 178 mm. It carries training readiness, improved training status, running power and Garmin running coach, plus music and a speaker. We rank it above the higher-scoring Suunto Race 2 because a marathon block needs its tools more than it needs 55 hours of battery in a 76 g case. The catch: no maps, and the shortest GPS-only figure of the Garmins here.

5. Suunto Race 2: the battery-life leader

Up to 55 hours in dual-band mode, up to 65 in single-band and up to 18 days as a smartwatch: no other watch here comes close. It adds offline maps with 32 GB of storage, ZoneSense intensity tracking and Suunto Coach. The cost is size: 49 mm across and 76 g, and Suunto lists the stock strap for 125 to 175 mm wrists. Most marathon training weeks won't use that much battery.

6. Suunto Run 2: built for race day

Suunto pitches the Run 2 at marathon training. Its Marathon mode shows a real-time finish prediction, and EnergySense estimates how much energy you have left. Dual-band GPS is rated up to 24 hours, with free offline maps and onboard music. The limits: Suunto says its adaptive training insights live in the app rather than on the watch, and the 46 mm case suits medium and larger wrists better than small ones.

7. Polar Vantage M3: recovery-first

Polar's pitch is recovery: Recovery Pro, Nightly Recharge and an orthostatic test sit alongside a Running Program tailored to race distance and Training Load Pro. Dual-frequency GPS is rated up to 30 hours in Performance mode, offline maps are preinstalled for North America and Europe, and Polar says the battery is fully replaceable. The drawbacks are up to 7 days as a smartwatch and no onboard music.

How to choose

• You want one watch that does everything: Garmin Forerunner 970.
• You want long battery and a light, compact case: COROS Pace 4.
• You want Garmin's maps and battery without the newest model: Forerunner 965.
• Your wrist is small: the 42 mm Forerunner 570.
• You want to charge as rarely as possible: Suunto Race 2.
• You care most about race-day pacing readouts: Suunto Run 2.
• You train by recovery data: Polar Vantage M3.

Still weighing the two biggest brands? Our Garmin vs COROS comparison covers the ecosystem differences. A marathon block is also when a shoe rotation starts to matter: our running shoe rotation guide explains the daily, long-run and race-day roles, and the Level Finder matches shoes to your weekly miles.

Marathon watch buyer's guide

Multi-band modes cost battery

Garmin, COROS, Suunto and Polar all list a multi-band or dual-frequency GPS mode, and all of them list fewer hours in it. The Forerunner 970 drops from up to 26 hours GPS-only to up to 21 with all systems and multi-band. The Pace 4 drops from up to 41 hours with all systems on to up to 31 in dual-frequency. When you compare watches, compare the same mode. When you train, you don't have to run every easy loop in the most demanding setting.

Maps or breadcrumbs

A breadcrumb trail shows the line of your planned route with no streets around it. Full maps show where you are and where you can turn. For long runs on roads you know, breadcrumbs are enough. For a 20-miler in a new town, maps help. The Forerunner 570 has neither preloaded nor downloadable maps on its spec list; everything else on this page lists maps.

Treat training-load numbers as advice

Training readiness, running tolerance, EvoLab and Training Load Pro all turn your runs and recovery into a suggestion. They're useful when mileage climbs week after week. But the plan comes first. Higdon's guidance to novices is to keep long runs conversational and that "there is no such thing as 'too slow'", and no watch score changes that.

Don't expect GPS to match the course

Wrist GPS isn't exact, so your watch and the race course will rarely agree to the tenth of a mile. A 2020 validation study of eight sport watches (Apple, Coros, Garmin, Polar and Suunto models of that time) found mean absolute percentage errors of 3.2% to 6.1%, with distances generally underestimated in urban and forest areas. On race day, treat the watch's distance as close rather than exact, and don't chase a pace number that drifts.

Mistakes to avoid

• Buying the biggest battery by default. The Race 2's 55 hours is impressive, but you wear its 76 g and 49 mm every day of an 18-week plan.
• Leaving the always-on display on and blaming the battery. COROS rates the Pace 4 at up to 19 days of daily use, or 6 with always-on display.
• Learning the watch on race morning. Set up your race screens and pacing features during a long run in the build, not at the start line.
• Skipping the half first. Higdon's Novice 1 Half Marathon builds the long run to 10 miles over 12 weeks and notes that "GPS watches make measuring courses easy." It's a good way to learn a new watch before the full.

Fit and sizing

Marathon watches run larger than beginner ones. The cases here range from 42.4 mm (Forerunner 570, small version) to 49 mm (Suunto Race 2), and the weights from 32 g (Pace 4 on nylon) to 76 g (Race 2). If you have a small wrist, the 42 mm Forerunner 570 and the 43.4 mm Pace 4 are the two to try first. Suunto lists the Run 2 for wrists from 130 to 200 mm, and the Race 2's stock strap for 125 to 175 mm.