Burning calories on those cardio machines

Those of us who have ever used a cardio machine have probably asked the question: Is the calorie count on cardio machines accurate?
I have wondered this. And I decided to do some research to get my answer.
I read through many web sites and they pretty much said the same thing. No, the calorie counter is not accurate.
The machines can overcalculate by as much as 30 percent. But most of them probably overestimate by 10 to 15 percent.
I also read that we shouldn’t rely on the numbers being so accurate. But we should take it more of how scale the gauge of your progress. This makes a lot of sense to me. I was also reminded that we shouldn’t obsess over the numbers.
I notice on the espinner if I do the Race Day workout, which is focused on speed and strength, my calories burned are much higher (like the picture to the left). If I do Endurance training, which is focused on moderate resistance and moderate speed, my calories burned are about 40% lower.
According Sparkle.com, using a heart rate monitor is the most accurate and convenient way to assess your exercise intensity. REI helps you choose a heart rate monitor that best fits your needs. This article on Livestrong.com gives detailed information how how to calcuate calories burned based on heart rate.
But according to everything I read, you will never get an exact calorie count. Because your body composition helps determine how well you burn calories, according to Livestrong.com.
According to RunningTimes.com, the caloric tally is often based on the average 150-pound male. Moreover, even if you fit this build your calorie expenditure could be quite different
According to MunFitnessBlog.com, these factors come in to play when your body is burning calories:

• Body size – If the machine does not ask for your body weight, most likely the calorie count is not accurate. A 50 kilogram person will burn less calories than person who is 80 kilogram, assuming they run on same pace with the same duration.
  
• Body composition – Also consider that a person who has a high percentage of lean muscle will burn more calories than a person with less muscle, because lean tissue is more metabolically active.
  
• Workout intensity – The higher the intensity, the more calories you will burn.
  

• Technique – Your workout will be more effective if you swing your arms at your sides, instead of holding the bar. Hanging onto the handrails will reduce the number of calories burned by 40 to 50 percent if you are using treadmill.

• Familiarity – The more familiar you are with an exercise, the fewer calories you use at the same level of effort. Your body may have got used to the cardiovascular exercise and therefore less challenge your body has to work and fewer calories you will burn. That is why it is good to do different cardio at different days.

• The machine – Without good maintenance, machines may get out of calibration. So, the figures you see on the screen can be way out of the real range.

• The manufacturer – Even if everything stays the same, the amount may still be different depending on the manufacturer of the equipment. This difference is possible because companies use their own formulas to calculate what an average person of a given size will burn at a given level of intensity.

I wish there was a quick and easy answer to this question. But after hours of searching on Google and reading, apparently there isn’t.
_These web sites contributed information, knowledge and research to this post: WebMD article on CNN.com, About.com, Washington Post.com, Sparkle.com._