tissue culture split... help please!

[geminikki]

i'm used to working with plates, but have just started working with large-volume suspended cells...
I used to figure a seeding concentration by taking desired conc./current cell count. However, that doesn't work with say, a 3L culture. V1*C1=V2*C2 is just not working for my brain on this! Should I calculate this as (desired conc./current cell count)*3000ml?

please help, I know it's a silly thing to be struggling with...