Garmin Forerunner 405 (Read 3619 times)

26.63 mi for the marathon seems pretty accurate to me. Not many marathons have the blue line that shows you the exact 26.2 mi that was certified. Plus if the course does have it how many people other then the elites stick to it. Maybe that person ran wide around some of the turns and that caused the difference in distance. When you’re talking about .05 of a mi difference that really isn’t much. Beats doing it the old way by driving it in your car. plus that could be off to.

About 1.5% out. That's pretty accurate by my books.

Personally, I've used and own a 305 & a 405. The 405 I'm finding is almost exactly .05 off on almost every run from the 305 - varying by length of run. My running parter also has a 405 and we are always exactly .03 off from each other starting & stopping at the same time.... My brother and his training team are experiencing the exact same inaccuracies. I've been doing a bit of back & forth with Garmin who says "the 405 is 95% accurate".... I heard another experience with the 405 stating it clocked her marathon at 26.62 miles.... not ok with me I'll update when I hear more from Garmin Good luck! Suffice to say.... the 305 is proving more accurate for me & my running partner & my brother

Accuracy is measured as how close something is to the truth, the gold standard. What is the gold standard against which you (and others) are comparing these devices when judging their accuracy? Course certification certifies that a course is AT LEAST a length, but it can be long. A certified marathon can be more than 26.2 miles. Perhaps 0.6 miles long. If that is your gold standard, then your gold standard too may be inaccurate. And what Marcus said.