Calorie Counts on Cardio Machines by Liz Neporent discusses what you need to look for to determine the accuracy of the calorie count you get from carido machies. Here are the highlights:
1. The calorie counter on any device is, at best, an estimation of your work output.
2. At the minimum, the machine's information panel must allow you to enter your weight, since the bigger you are, the more calories you burn -- no matter what you're doing. If the machine doesn't ask you to enter your weight, the information is useless.
3. Even if the machine factors in weight, it still can't account for variations in muscularity and cardiovascular efficiency between people of similar weight.
4. None of those machines factors in individual fitness levels and the specificity of the exercise.
5. The numbers that you see apply only to you, and only for that particular piece of exercise equipment. You can use the readout to compare workouts on that machine, but don't try and correlate the information you receive from two different types of equipment.
6.Use a heart-rate monitor for a more accurate feedback.