You need to add up the total Unit IPC value for each side (land and naval, not including ICs). If it’s a tie at the end of the Russian turn (or if the Axis is ahead), then the Axis is very likely to win the game. You can do this automatically if you are using a program like aBattleMap.
I developed a statistical model for predicting game outcomes which is pretty accurate (100% accuracy on my small sample of games, starting on round 5):
http://www.campusactivism.org/blog/node/189