treadmill calorie burn counters

I have a treadmill that has a calories burned counter.  Does anyone know how accurate these things are?  The problem that I am having is that I always run on an incline of 3.5 - 5.0 and when I try to look this up on cc running is only listed in a flat level surface, but I know I have to be burning more calories with the extra incline, right? 

Should I go by my treadmill or by something else??? 

I always go by what the treadmill says.

Depends on the treadmill. At my old gym, I always found the ellipticals and treadmills were pretty consistent with what CC said. But if they are older and uncalibrated, or didn't ask you at least for your weight, then they might be off.

I know mine is way off. I finally got a HRM for xmas & wore it on the treadmill. The treadmill said I burned 530 cals & my HRM said around 370. My treadmill doesn't let you enter your height & weight though so that may make a big difference too.

thank everyone!  My treadmill does not let me enter in my weight and height either, so maybe I should get a heart rate monitor?  What is the best way to figure out burned calories?

thanks in advance for your help!

I figure that the calories the treadmill show are burned are about what an average, 150 lb female would burn, so I multiply my weight by the number of calories the machine says and then divide by 150. It usually is pretty accurate...hope this helps!