As noted by TechCrunch, Google has recently added elevation data to bike routes in Google Maps. Google confirmed the new feature, which it left out of announcing in its big Maps updates earlier this week.
Just look for a route on Google Maps, choose the biking directions and look for the new elevation profile. Besides the graphical representation of those hills you will have to climb, the new card also shows you the total number of feet you will have to climb on your route (and those joyous miles you get to just kick back and try not to die while you barrel down the hill on the other side).
The new elevation data is available in Google Maps when looking at biking routes on the desktop (except for routes that happen to be mostly flat), but the feature is unfortunately not yet available to users of the Maps mobile apps.