the title is probably somewhat cryptic, so I'll try to explain what I mean

I've already learned some chess tricks which make calculations in a game a bit easier (especially speed games which I play a lot) because they help to quickly evaluate if - for example - the king can stop a pawn from promoting ("the square"), or who will get opposition (odd or even number of squares between kings) etc.

My question is if there's any good method of calculating the outcome of a series of exchange

I am still getting lost when there is a lot of attackers and defenders, I start imagining "OK bishop takes knight, pawn takes bishop, knight takes pawn, queen takes knight, rook...", and I have a hard time to say who'll be better off at the end

is there any handy trick for that or only blood sweat and training

I just count how many pieces are attacking the square. It really doesn't matter what order the pieces are traded if you are simply trying to take the square. You've simply got to have more pieces aimed at the right square.

After you've decided that the number of pieces is a go, make sure the material exchange is what you are willing to take. After those two areas of concern have been taken care of, then you can work on the order that you'd like to attack.

NM Dan Heisman has written about this type of thing in his excellent Novice Nook column at chesscafe.com. Check out these articles:

http://www.chesscafe.com/text/heisman15.pdf
http://www.chesscafe.com/text/heisman75.pdf

--Fromper

i think the calculating method of after a series of moves, you erase in your thoughts the captured pieces, then begin to calculate again if it is necessary is good, by doing this it will help you to calculate longer

I've just taken a look at Lasker's Chess Strategy and felt rather proud of myself. On page 16 he suggests the same system that I described, just count how many pieces are attacking and defending the square. I read the passage, remembered the thread and wanted to say that Lasker agrees with me!

Lasker was a giant for sure. (Emanuel, not his accepted brother, by some.)

First thing in Tactics should be personal "King Safety". Then captures, Threats, and then quiet moves which yield dividends...

in general the exchanges should start with lower valued pieces.jmo