So the last few days, I've been trying to use multiple apps each time I work out. Earlier this week, I did a 4.5 mile outdoor walk using the Workout app and Runkeeper simultaneously. At the end, I found that Runkeeper was about a tenth of a mile ahead of the workout app, and said I burned double the calories. Then, I did a treadmill run a couple of nights ago that the Workout app said was 1 mile, but the treadmill itself said it was only .86 miles. Just curious of anyone else's results, and any thoughts you may have.