This is pretty simple...
Initially, just forget about the premium paid or received.
Then think about it in terms of long or short total legs across the spot values, where the breaks/turns are at the strike.
So for instance:
-1/+3 50-40 put ratio, premium received of 0.50 (credit).
Breaks at 50 and 40, below 50 short 1 put, below 40 long 2 puts...
So excluding the premium, BE-1 is 50 and BE-2 is 35. (strike - 10/2 (which is strike diff / net position) Max loss at 40 of -10.
Including the premium, BE-1 is 49.50 and BE-2 is 35.50, Max loss at 40 of -9.50
Hmm... I guess it's more like second nature for me, takes a bit of practice....