I ran the London Marathon with the Garmin Forerunner 970 vs Coros Pace 4 — which was more accurate?

Wellness Smartwatches I ran the London Marathon with the Garmin Forerunner 970 vs Coros Pace 4 — which was more accurate? Features By Nick Harris-Fry published 28 April 2026 Both watches impressed on race day When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. (Image credit: Future) Jump to: Verdict Copy link Facebook X Reddit Email Share this article 0 Join the conversation Follow us Add us as a preferred source on Google Newsletter Subscribe to our newsletter I’ve run the London Marathon nine times and if there’s one thing I’ve learned from all those races it’s that having one of the best running watches on your wrist can help you train for and pace the event.Over the years I’ve noticed a clear improvement in the GPS accuracy on top watches in the race, especially around the skyscrapers in Canary Wharf, and the reliability of optical heart rate sensors has also got better.This year I used the Garmin Forerunner 970 and Coros Pace 4 on race day, having also used them for months of training for the London Marathon.Article continues below You may like I raced a half marathon with the Garmin Forerunner 970 vs Coros Pace 4 — here’s the winner I ran a half marathon with the Apple Watch Ultra 3 vs Garmin Forerunner 970 to test the GPS and heart rate accuracy — here’s the winner I wear a Garmin watch for marathon training — these are the 5 stats I care about and the 3 I ignore Both are great options for runners and performed well during the race — here’s how they compared for GPS, heart rate and race prediction accuracy.Garmin Forerunner 970: was $749 now $649 at AmazonThe Garmin Forerunner 970 is the best running watch you can buy in my opinion, with a lightweight, attractive design and all the features you could ever need. It's rarely in sales but right now two colors of the watch is reduced to $649 at AmazonView DealCoros Pace 4: $249 at AmazonThe Pace 4 is perfect for runners and triathletes who want a small, accurate watch with a bright display that's also great value. It comes in either black or white and with either a silicone or nylon band — I'd go for nylon to make the watch even lighter. The new Black Crystal model of the watch has an aluminum bezel to make it feel more premium.View DealGPS Accuracy (Image credit: Future)Both watches recorded a total distance that was impressively close to the official marathon distance of 26.219 miles, though the Garmin Forerunner 970 was closer to this.I did have to weave around some runners early on but was mostly able to run the optimal racing line, which is marked on the road in the London Marathon, so I probably ran close to the official distance on the day. (Image credit: Future)Both watches were hitting mile splits quite close to the markers on the course too, though I did reset the lap counter a couple of times to bring them nearer in line to the markers. window.sliceComponents = window.sliceComponents || {}; externalsScriptLoaded.then(() => { window.reliablePageLoad.then(() => { var componentContainer = document.querySelector("#slice-container-newsletterForm-articleInbodyContent-V2qDgHCMzTmRFBXsx6tLF6"); if (componentContainer) { var data = {"layout":"inbodyContent","header":"Sign up to get the BEST of Tom's Guide direct to your inbox.","tagline":"Get instant access to breaking news, the hottest reviews, great deals and helpful tips.","formFooterText":"By submitting your information you agree to the <a…

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