The Garmin Venu 4 and the Apple Watch Ultra 3 are sure to make our best Garmin watches and best Apple Watches lists, respectively, as we wind up the last crop of 2025 releases and head into 2026.
Having just strapped on the Garmin Venu 4 at time of writing, it’s already shaping up to be a terrific watch. Its 45mm model is light for its size, it’s bright, and I look forward to testing it over the next 10 days.
As part of my review process, I’m testing its heart rate sensor’s accuracy against an industry-standard Polar H10 Bluetooth heart rate monitor, along with using the very accurate Apple Watch Ultra 3 as a ‘control’ watch during the experiment.
The Polar H10 was rated the best heart rate monitor for accuracy by us and many, many others. By general consensus, it’s a top-flight piece of kit, and one used by many professional athletes. When I put the strap on, it interfaces with the Polar Flow app via Bluetooth, broadcasting live heart rate readings to my phone.
I’m using the Polar H10 to test the accuracy of Garmin and Apple’s heart rate readings during my 7km lunchtime run. Below in the gallery of screenshots, you can see how each app recorded my run, factoring in a pause for all three apps about 10 minutes into the workout. Unlike the picture above, in which I’m wearing both watches on the same arm, I’m actually wearing a watch on each wrist to better record HR.
The workout: results
The Garmin Venu 4, surprisingly, wasn’t very accurate at first. When I checked both watches somewhere between 1km and 2km, I was surprised to see that I was getting very different readings: Apple said my heart rate was in the 140s, while the Garmin Venu 4 said I was in the 120s. You can see the dip on the graphs below. I carried on for a bit, then paused both watches while I checked the Polar Flow app.
Sure enough, Apple had the right of it, and was a lot closer than Garmin. I knew the Apple Watch was accurate thanks to my earlier cycle test, but I was surprised that the Venu 4, fitted with Garmin’s top-line Elevate V5 heart rate sensor, was so far out. I restarted all three apps and carried on. I did not remove, adjust or restart my Garmin watch.
After pausing and unpausing, the Garmin Venu 4 was far more accurate, matching the Apple Watch Ultra 3 much more closely for the remainder of the run. You can compare the graphs and see that when I resumed the workout, my heart rate on Garmin Connect is recorded as being higher.
By the time I had finished, my average bpm according to Garmin was 151bpm, not far off the 156pm recorded by Apple and Polar.
I ordinarily wouldn’t sniff at a 5bpm difference, considering that perfectly fine and accurate enough for most runners, but that initial gulf was interesting. I’ll conduct further accuracy tests, and if I notice any more drastic differences, I’ll reach out to Garmin for clarification.
In the meantime, over the course of 7km, I’d say for the most part the Venu 4 was very accurate, and would have been even more accurate if I’d continued to run for a longer distance, to make up for that initial blip. Stay tuned for our full Garmin Venu 4 review.
