Originally Posted by merlinextraligh

40 calories a mile would appear to be a gross generalization. Depends so much on the terrain, the speed, the rider's aerodynamics, pack or solo, etc.

15 mph, flat ground is not going to hit 40 calories. 20mph in a pack, flat ground is likely still under 40 calories.

25mph TT effort is likely above 40 calories a mile.

Climbing 10% grade is clearly above 40 calories a mile, descending well below that.

YCMV