Cycling on Gym bike

I'm confused about the amount of calories I'm burning here. I work for 30 minutes on "level 5 workout" (the intensity is always changing every 2-4 minutes) so I always put "Bicycling - 12-13.9 Mph, Leisure, Moderate Effort" and it comes to 597 calories. However, on my bike monitor it claims I've only burned 150 calories.  Should I trust calorie-count more or my gym bike's monitor?

Calorie-count way overestimates the calorie burn from bicycling (by as much as a factor of two in some cases).

Does your gym bike show wattage?  If so, you can take the average power and the time and compute the calories burned to see if it agrees with what the gym bike is telling you.

kCals burned = average power * (seconds / 4186.8) / 0.25

That is, average wattage times seconds spent exercising, divided by 4186.8 to convert Watts to kCal, and finally dividing by cycling efficiency, which is at most 25%.

Uh well, I'm no good at math. I did exactly what you said and came up with: 8.598452278589853826311263972485

Since you said they're kCals, I'm assuming I should convert them to the calories that I understand.  I got: 8598.452278589853 from this website converter tool. (http://www.convertunits.com/from/kcal/to/cal) That doesn't make sense that I'm burning 8,598 calories in 30 minutes??

But if I shouldn't convert them, basically 9 calories right? =/ In 30 minutes? Its such an intense workout for me.. I can't believe its ONLY 9 calories. I sweat so much. I must have calculated this wrong.

The power levels I have are:
2-2-3-3-5-5-8-8-8-8-2-2-4-4-6-6-9-9-9-9-4-4-6 -6-8-8-3-3-2-2

Could you please try the equation out for yourself and tell me what you came up with? Anyone out there willing to help me? =[ I'm so confused!

The equation seems to work out for me-- 10 minutes of cycling at 100W goes like so:

kCals burned = 100 * (600 / 4186.8) / .25

kCals burned = 100 * .143 / .25

kCals burned = 14.3 / .25

kCals burned = 57.3

And that sounds fairly reasonable to me, although I can in no way say if that's accurate. It works out to about 344 calories an hour, and that's only 30 calories less than CC says I'd burn. The equation, unlike CC, does not factor weight in at all, so maybe that's where the discrepancy lies. Hopefully my step-by-step for the math will help you-- remember that you'll be doing it for about 150 watts, as that equates to moderate effort.

As for the 597 calories, are you certain you aren't looking at the amount for a whole hour? For moderate effort biking mine says 544 for an hour, so for it to give you 597 for half an hour, I think you'd have to be too large, tall or wide, to even use a gym bike.

Calorie Count uses a lookup table that appears to be based on an article from Bicycling magazine from several years ago.

I use a power meter on my bike; thus I know what my calorie burn is for a given duration and a given effort.  You have to work reasonably hard to burn 597 kCal/hour--that's roughly an average of 170 Watts, and for most people, that's pretty hard to sustain.

I find that, for either a hilly route or an exceptionally windy day, picking the cycling speed one category below what I actually did is a closer match to my actual burn than is the category into which my average speed really falls.  For easier routes or less windy days, I have to pick two categories slower.  For a recovery ride, three categories slower.

That's not an answer that people like to hear, but the bathroom scale does not lie.  If I use CC's numbers and eat accordingly, I do not lose weight.  If I use my power meter's numbers and fudge CC to make it match my power meter, I lose weight at the expected rate for the deficit I see on CC.