How to determine Brewhouse efficiency

Hi guys.
I've been All Grain brewing for some time & I just need to confirm how to correctly calculate Brewhouse efficiency.
If I have a recipe that is a 23 litre batch set @80% efficiency, at the end of boil I should have 23 litre batch size @1.052, is this figure the total wort I have made on the day, 20 litres into my fermenter + 3 litres of trub = 23lt total ) or is it the actual volume I get into my fermenter.
23lt total - 3lt of trub = 20lt of wort made @1.052.
Cheers

Brewhouse efficiency is figured off the volume you get out of your fermenter. Beer smith forum has several post that discuss this in detail. (all losses from mashing and fermenting, boil off rate, mash efficiency.)

I found some good info in this thread. http://www.beersmith.com/forum/index.php/topic,5140.0.html