Pace Hare

Triathlon

Best watches for ultras and Ironman

Published GPS claims here run from 43 h to 75 h, and all are the makers' own figures in different modes. Fenix 9 and Enduro 4 have no comparable figure, so they get no bar.

By Pavel Ryzhikh, 3 November 2026. Prices checked 3 November 2026.

Drawing for the article: Best watches for ultras and Ironman
GPS battery, in hours

  1. Suunto Vertical 2

    Best for the longest ultra, on claimed hours

    Suunto claims 75 h of all-systems GPS on single-band and 65 h on multi-band, the longest figures here. At 87 g and 49 mm it's the heaviest on this page, and Suunto lists preconfigured multisport modes.

    £529 on suunto.com (UK), checked 3 November 2026.

    See it on suunto.com

  2. Suunto Race 2

    Best for an Ironman with hours to spare

    Suunto claims 65 h of all-systems GPS and 55 h on multi-band, and it lists open-water swimming and multisport modes. It weighs 76 g on a 49 mm case, and sensors connect over Bluetooth only.

    £429 on suunto.com (UK), checked 3 November 2026.

    See it on suunto.com

  3. Coros Pace 4 Pro

    Best for a long race at a lower weight

    Coros claims 60 h of all-systems GPS and 40 h dual-frequency at 51 g with silicone, or 43 g with nylon. Sensors connect over Bluetooth only, so an ANT+ only power meter won't pair, and DC Rainmaker got well under a different Coros battery claim.

    £389 on coros.com (UK), checked 3 November 2026.

    See it on coros.com

  4. Polar Vantage V3

    Best for a first Ironman on Polar Flow

    Polar claims 43 h of GPS in Performance training mode at 57 g, with maps and dual-frequency GPS. It's the shortest figure on the bar, and it won't take ANT+ sensors.

    £415.20 on polar.com (UK), checked 3 November 2026.

    See it on polar.com

  5. Garmin Enduro 4

    Best for ultras if your data lives in Garmin

    Garmin's UK page lists Activity Mode hours from Max Accuracy to Max Battery with no plain GPS-only figure, so there's no comparable number and no bar. It's 66 g with its band on a 51 mm case, with ANT+ and Bluetooth.

    £799.99 on garmin.com (UK), checked 3 November 2026.

    See it on garmin.com

  6. Garmin fēnix 9

    Best for Ironman on Garmin with a 10 ATM case

    Garmin's Activity Mode hours for the 47 mm version run from 25 h in Max Accuracy to 81 h in Max Battery, with no GPS-only figure, so there's no comparable number and no bar. It's 75 g with its band for the 47 mm version, with ANT+ and Bluetooth.

    £859.99 on garmin.com (UK), checked 3 November 2026.

    See it on garmin.com

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Every hour in the table is a maker's claim. I haven't worn any of these watches, and the one independent battery check I found doesn't flatter its claim. DC Rainmaker (non-peer-reviewed) got under 20 h, sometimes the low 20s, from a Pace 4 Pro against Coros's 30 h claim with Max GPS and an always-on screen. Coros promised a fix in November, and I couldn't confirm it has landed. The figures were checked on maker pages on 3 November 2026.

That matters for the only question this page asks: will the watch still be recording when you finish?

Published hours, side by side

Watch

GPS, manufacturer claim

Multi-band, manufacturer claim

Suunto Vertical 2

75 h, All systems, single-band

65 h, All systems, multi-band

Suunto Race 2

65 h, All systems, single-band

55 h, All systems, multi-band

Coros Pace 4 Pro

60 h, All systems (High)

40 h, All systems, dual-frequency

Polar Vantage V3

43 h, Performance training mode

No separate figure

Garmin Enduro 4

No comparable figure

No comparable figure

Garmin Fenix 9

No comparable figure

No comparable figure

Read the first column with care. Suunto and Coros both quote all satellite systems, while Polar's figure is its Performance training mode. Those aren't the same test, so a few hours' gap between two brands proves little. The same goes for the bar at the top of this page.

Why the two Garmins have no bar

I'm not going to invent a number for them.

Garmin's UK page for the Enduro 4 has no plain GPS-only figure. It has Activity Mode settings instead, and they vary a lot on one watch: up to 60 h in Max Accuracy, 80 h in Normal and 210 h in Max Battery, all before solar. All of those are manufacturer claims. Garmin's press release leads with up to 320 h, but its footnote assumes extended battery mode and continuous 50,000 lux, which says little about a night section.

The Fenix 9 page uses the same Activity Mode wording: for the 47 mm version, up to 25 h in Max Accuracy, 30 h in Normal, 37 h in Extended Battery and 81 h in Max Battery, all manufacturer claims. Its manual says those modes use SatIQ to pick the satellite systems. Neither maps onto the single-band or all-systems figures from Suunto and Coros, and neither sits fairly beside Polar's mode.

Both could well last your race. I just can't put them on a scale against the others, so they appear with no figure.

Ironman: the sum is short

Most Ironman events have a limit of 16 or 17 h, according to Wikipedia's entry, and your athlete guide has the one that counts. Take 17 h as the worst case.

Every watch with a figure in the table claims more than double that on its main mode, and the Fenix 9's lowest listed mode also claims more. The Pace 4 Pro's multi-band claim also clears it comfortably. So for a one-day Ironman, I'd stop reading the top of the list and look elsewhere: weight on the swim, whether your sensors connect, and which app you already train in.

Sensors can settle it. The Suunto Race 2, Coros Pace 4 Pro and Polar Vantage V3 list Bluetooth only, so an ANT+ only power meter won't pair. The two Garmins take both. If you're moving up from a shorter race, Polar Vantage M3 vs Forerunner 570 covers watches built for shorter races, and the triathlon goal page has the wider list.

Ultras: work from your slowest finish

Here the hours start to count.

Take your slowest realistic finish, including sleep stops and aid stations. Then I'd want the claim to beat it by at least half again. That margin is my own rule of thumb, with no measurement behind it, and it exists because these are makers' figures from their own test conditions.

Navigation, music and a brighter screen could all cost you hours, and the makers' figures don't tell you how many on your route. If your race needs multi-band for a deep canyon or heavy forest, use the second column. It's lower on every watch that lists it.

Whether multi-band earns that cost is an open question. The nearest peer-reviewed distance study, Gilgen-Ammann 2020, part-funded by Polar, tested 2019-era watches and found errors worst in cities and forest, with no multi-band receivers among them. I found no independent peer-reviewed figure on what multi-band adds. Multi-band GPS explained covers when it might help, and how to choose a GPS mode turns race length into hours.

What I'd buy

For a multi-day ultra where hours decide everything, the Vertical 2 has the longest published figure, if you can live with 87 g on your wrist.

For an Ironman, the Race 2 has hours to burn, and it's the one I'd check first on Bluetooth-only kit. The Pace 4 Pro does a similar job at 25 g less on the silicone band, if Coros fixes the battery drain DC Rainmaker measured.

Already on Garmin, with years of data and ANT+ sensors? I'd understand choosing the Enduro 4 or Fenix 9 anyway. Just know you're buying on Garmin's mode tables, with no like-for-like figure to compare. Other options sit on the products page.

Sources