The sites seem to work great for measuring calories in food, but I agree that they are wildly inaccurate and variable on calories burned. This is because variable is stacked upon variable, increasing error. It isn't like they stick some kind of power meter on people of all different ages, fitness levels, body fat composition, bone density, and who are riding fat tire bikes or skinny tire bikes up hill or down or with a head wind or tail wind and then make a calculator. Even so, it is interesting that the estimates seem invariably high.
