Tricks to calculate true count in Double deck game?

Whats the best or easiest way to caclulate the tc in a 2 deck game? Say 1 3/4 remain, 1 1/2 remain, 1 1/4 remain, or 3/4 remain.
I was thinking today when 1.5 remain to split the rc in half then add half of that number so if rc is 14 split to 7 then add 3.5 so tc is 10 is this the best way to do it when 1.5 decks remain? Any other ideas or tricks greatly appriciated?
Thanks.