my apple watch distance is way off

Good news! Thanks for the update

I was having the same problem as everyone else here while using watchOS 1.x until I followed the workaround mentioned by dacheng81 upthread to turn off "Motion Calibration & Distance". That fixed the problem for my outdoor walks. I believe what was happening is that the watch determined a calibration of my stride using the GPS in the first few walks, but then as I increased my pace, and consequently my stride, that caused the under-reporting of distance when the watch switched over to not using GPS (even though I had my phone with me at all times). The workaround causes GPS to be used always, then the distance is accurate. However, when I went on an outdoor bike ride, the distance and speed were both reported was zero! That's counter-intuitive since the bike ride should always use GPS, but apparently turning off the setting prevents it. So, to use that workaround required changing the setting for each activity.

Now I have updated to watchOS 2, but I have not yet gone back to the default setting. For those of you testing with watchOS 2, do you have "Motion Calibration & Distance" turned on?

Nope, I think the problem is not fixed. Today I walked a route that I believe to be 3.98 miles from multiple earlier walks with the motion calibration off and it was reported as 3.88 miles. This is a difference of 15'23" pace versus 15'00".

You'd need a better point of comparison that the "belief" that something was previously giving you an accurate value, when that something was an incredibly fishy "fix" to begin with.

While I don't have any calibrated measure of the length of my route, it seems to me that if the reported distance is consistent within +/- 0.02 over several walks of the identical route with the motion calibration turned off, but then is low by 0.1 on the second day after turning motion calibration back on, then that is a valid observation of a change in behavior. Yesterday was the first day with motion calibration turned back on, but unfortunately the walk was paused for 0.2 miles per Google maps (because I have trouble getting the pause icon to toggle consistently when I touch it). The recorded length of the walk without the missing 0.2 miles was 3.80 miles which is consistent with the 3.98 full length I have seen without motion calibration. If the watch performed calibration during that first walk yesterday and used it rather than GPS on today's walk, that would be a possible explanation for the underreporting I saw today.

You're right that none of this is absolute. We could be a lot more sure if Apple would just say how this works and/or make it work right.

Yes, it is a change in behavior, but consistency does not imply correctness. Without knowing what the behavior is changing from, you can't assert what it's changing to. My WATCH was consistently wrong on the same routes before, and the last three times I took it there (once, it was without my iPhone), it has been consistently right. How do I know what was right or wrong? By measuring the actual distance traveled, using something that did not involve the WATCH at all. You can't use the instrument you're trying to measure in order to prove that said instrument is exact.

I was having the same issues as everyone else, distances off significantly. I left on vacation to the beach this past Friday Oct 2 to the beach and for some reason my watch is now much more accurate with distance measurements. Here are the results: Oct 3 I walked 1.46 miles according to Map My Fitness App, Watch showed 1.44 miles. Oct 4 I ran 3.04 according to Map My Fitness App, Watch showed 3.01 miles. I then also walked 1.74 miles according to Map My Fitness App, Watch showed 1.73 miles. Oct 5 I walked 1.48 miles according to Map My Fitness App, Watch showed 1.47 miles. Today Oct 6 I ran according to Map My Fitness 5.04 miles, Watch 5.01 miles. So I can say that I am reasonably happy with the results now that I am getting on my watch. As a point of clarification, I attempt to stop the watch as soon as I stop running but, sometimes it is difficult to get the watch to stop immediately. This may lead to some variation in distances between Watch and Map My Fitness App. I wish we could set Watch to automatically pause when you stop moving like the Map My Fitness App does. Just further clarification I am using an iPhone 6S with IOS 9.0.2 and Watch with watch OS 2.0.

I agree. I'm on my second watch and I'm frustrated. My distance is always at least .25 off my Garmin, which means my pace is also incorrect. This doesn't work when training for a race when both distance and pace are important. I paid extra for GPS and it doesn't work correctly.