After suppressing Kurama's chakra with his own, he's left with 4 times more chakra than Kakashi. Now that he has befriended Kurama his pure chakra should be a lot more than that.
Enough for sage mode. Pa said that only Naruto can do it, in knoha there are users with 5 points in chakra, so he must be doble that. Like a 10 or more while 17
Fact Uzumaki have more chakra than Uchiha,Senju,Hyuga or any other people. Base Naruto will always have more chakra than the next Guy simply because its Natural for an Uzumaki to have it.