I wore the Apple Watch Ultra 3 for an entire marathon weekend and the battery life shocked me

As someone who usually wears a dedicated sports watch, where battery life is measured in days or weeks, the news that the Apple Watch Ultra 3 had six more hours of battery life didn’t sound that impressive to me.
However, I’ve used the Apple Watch Ultra 2 to run marathons before, and I know that Apple tends to be conservative in its battery estimates, so I was keen to see if the Apple Watch Ultra 3 could surpass the 42 hours it’s listed as lasting.
I had a trip to Inverness in Scotland lined up to run the Loch Ness Marathon, so I charged the Ultra 3 to 100% at 1pm on Friday afternoon to see how far through the weekend it could last.
The results were surprising, impressive and actually gave me a real shock. The watch didn’t run out of juice until Monday afternoon, just before I arrived home from the trip, and I had no fear of it dying during the marathon on Sunday morning.
Loch Mess Marathon battery test
I used the Apple Watch Ultra 3 normally throughout the weekend, with the screen always-on and for sleep tracking on Friday and Sunday night.
I did take it off for the night before the marathon because I don’t look at any sleep tracking info on the morning of a race, so it saved some battery then by automatically going into low-power mode overnight.
Along with the marathon itself I also used the watch to track my shake-out run on the Saturday, and I used normal tracking settings for those runs, not the low-power GPS. I didn’t listen to music using the watch on the runs though, which can be a big battery drain.
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On the morning of the race — 44 hours after I charged it — the watch still had 51% battery, meaning I was confident it would last the event without a top up.
I finished the race in 2:24, and when I checked the battery shortly afterwards the Apple Watch Ultra 3 still had 27% left.
Naturally, a longer marathon time will drain more battery life, but there was enough juice left for a few more hours of running when I finished.
When I woke up the next morning, the battery life was in the red, but it still lasted the flight home. I put it into low-power mode when it hit 2% and that got me another hour or so — you could definitely extend the life longer with some strategic low-power stints.
How does it compare to sports watches?
While three days of battery life including a marathon was impressive for the Apple Watch Ultra 3, you certainly can get more from the best sports watches.
I had the Garmin Fenix 8 Pro on my other wrist and it was still at 33% when I got home on Monday, having charged it to 100% at the same time as the Ultra 3. I also used the Fenix 8 Pro’s power-intensive LiveTrack feature during the marathon, which was sending my location to my family using its built-in LTE throughout.
Even smaller watches than the Fenix 8 Pro, like the Garmin Forerunner 970, will comfortably outlast the Ultra 3, but the Ultra 3 is a true smartwatch that’s more useful day-to-day — it showed my boarding passes for the flights to Inverness, as one example.
The Ultra 3 also charges incredibly quickly, and given that it now lasts over two days comfortably even with heavy use, you’re always likely to find a 30 minute window to charge it in that time.
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Nick Harris-Fry is an experienced health and fitness journalist, writing professionally since 2012. He spent nine years working on the Coach magazine and website before moving to the fitness team at Tom’s Guide in 2024. Nick is a keen runner and also the founder of YouTube channel The Run Testers, which specialises in reviewing running shoes, watches, headphones and other gear.
Nick ran his first marathon in 2016 and became obsessed with the sport. He now has PBs of 2hr 25min for the marathon and 15min 30sec for 5K. Nick is also a qualified Run Leader in the UK.
Nick is an established expert in the fitness area and along with writing for many publications, including Live Science, Expert Reviews, Wareable, Coach and Get Sweat Go, he has been quoted on The Guardian and The Independent.
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