There are minor alignment spoilers for my group below, read at your own risk. The process for calculating the following involves adding each persons level, charisma reaction adjustment, and alignment modifier together. Then, Chaotic and Evil values are made negative. Then the totals for law/chaos and good/evil are added excluding neutral values to get a numerator. Then the totals are calculated as absolute values to get denominators. Then you divide out the fraction and check a table to find the party alignment.
The point of all this was that I was convinced that the party had a lawful evil drift, and it turns out, the party is straight up neutral. This might have to do with the extreme numbers of wildly divergent alignments. Right now external pressures are keeping these things in check, but once those (eventually) disappear, there will certainly be some conflict.
Numerator total for LAW/CHAOS = 29
Denominator total for LAW/CHAOS = 93
Numerator total for GOOD/EVIL= -17
Denominator total for GOOD/EVIL = 97
LAW/CHAOS is .31182
GOOD/EVIL is -.17525
Checking table 4A in the GMG, the party alignment is true neutral (with a drift towards lawful and evil).
If you just take the actual PC's, you end up with (22/51)(-13/52)
LAW/CHAOS is .43137
GOOD/EVIL is -.25
Leaving the party with a group alignment of lawful neutral (with an evil drift)
The table is quite simple. Anything over .33 is Lawful, anything under -.33 is Chaotic. Anything between is neutral. The same is for Good and Evil.