I did a 13 mile run this morning and another 5 this afternoon and I burned 1576, according to the site. I'm also at 8000 feet of altitude and am running in hills and am probably doing it faster than it thinks. But all it asks me for is my weight and mileage. There's no way it can be accurate. I've ate at least 4,500 calories today. (I'm at a running camp right now btw)