EDIT: I realized original formula was wacky--was trying to not count employer contributions as my own savings, but I actually ended up counting it against me.
I'll give this one a try, although I may need to figure out a better tracking system. As a quick and dirty estimate for March, I did:
Income = Net pay
Savings = Mortgage principal + my 403 contribution + my HSA contribution
Result = 77%
Maybe I need to shoot for the 80%!