I use My Fitness Pal to determine my calorie budget. Even choosing sedentary, if I follow their guidelines, I will not lose weight. I have determined I have to have my goal set at lose 1.5 pounds per week in order to maintain my weight. I let MFP keep track of the calories I burn while biking but I don't eat back my daily rides. Even my longer weekend rides, I don't eat back all the calories. This is the only way I seem to lose weight.
My guess is that my metabolism in the toilet from years of dieting. And the only way to really determine what my BMR is to undergo expensive testing.