Use Google Earth (which is different from Google Maps). It's free to download.
Once you put the route in, right click on the line and select "profile". It will show an estimate of the grades along the route. We've found it fairly accurate.
I'm on the website but don't see any sort of "route" option... ah, sorry, missed the download part. Wow, that is pretty cool. The google earth pc app is a resource hog but its otherwise very effective for elevation as described.
Wish the app had the same function but I'll take it!
Cheers.
