I like round numbers, so lets say that we've got 26 lowercase, 26 uppercase, 10 numbers, and 18 symbols, for a total pool of 80 character options. For our singl

I like round numbers, so lets say that we've got 26 lowercase, 26 uppercase, 10 numbers, and 18 symbols, for a total pool of 80 character options. For our single lame character, you're stuck with 26. All calculations are rounded off to make them a bit less insane to read. Assuming a 10 character password, there are 1.07 × 10^19 combinations without the restriction, 3.5 × 10^18 combinations with the restriction. If we're dealing with a 24 character password, like my password manager slings out, it's 4.7 × 10^45 vs 1.5 × 10^45. As you can see, it definitely reduces the keyspace, but when you look at the overall impact it's rather small.