Originally Posted by aaronmcd

Idk... internet somewhere. It must be accurate.

http://www.ncbi.nlm.nih.gov/pubmed/18803095 efficiency = 0.257 ± 0.0245
http://www.ncbi.nlm.nih.gov/pmc/arti...394253/?page=4 efficiency = 26.1%
Random term paper I found cited 22% - 26% from:
Prempero, Pietro. “Cycling on Earth, in Space, on the Moon.” European Journal of Applied Physiology, 2000, 82: 345-360

Using 26% from the first 2 sources that closer agree:
1 kJ = 4.2 kcal, so accounting for human metabolic efficiency on the bike, 1 kJ → 1.09 kcal