Calculating memory allocaiton per process

Howdy,

Is there a doc somewhere that has a formula for how much memory PG backend process will use?

I'm looking to get something like total_mem = max_connections * ( work_mem + temp_buffers )
// I know it's more complicated than that, which is why I'm asking =)

Something similar to Table 17-2 here: http://www.postgresql.org/docs/9.0/interactive/kernel-resources.html
would be awesome.

Dave