Bicycle Mechanics - Need help with proper chain length

I have assembled all the parts neccessary to complete the bike then came the chain. I bought me a chain tool for my 10 speed campy chain but i don't know how long the chain would be. I am using a 53/39 chaining and a 12-25 cassette with a short cage record derailleur. Can anyone tell me what the right chain length would be and how will i be able to determine if i have the right chain length?

wrap the chain to large ring in the front and large sproket in the back plus two more chain link, that is the length of your chain

Do this just around the cogs, without running the chain through the rear der.

Park Tools website has several formulae for working this out.

See http://www.parktool.com/repair_help/FAQchainlength.shtml
Remember to account for the master link, or extra links on the Campy system.

If you don't know enough to size a chain properly, you don't know enough about building a bike to do it properly, especially for campy 10-speed stuff. At the very least, take it to a bike shop and have them check if you did it right.

I do the big/big +2 thing then I take some white out and mark the link.

I then run the chain through the derailleur and hold the two ends together with a bent spoke (bent into a u-shape) and put it into big/big again. I check to see how much tension is on the rear derailleur. If it's pulled too tight, I add a link.

I then, carefully shift and move the chain with my hands into the small/small combo. If the chain is too long, the chain will drag around the bottom jockey pully and accross the upper pulley. If this happens I remove a link.

Between the two, it's better to have a chain one link too long then one link too short. You should never cross-chain your drivetrain anyways, but if you do get into the big/big combo with a "too short" chain, you could damage your rear derailleur.

L8R

If you don't know enough to size a chain properly, you don't know enough about building a bike to do it properly, especially for campy 10-speed stuff. At the very least, take it to a bike shop and have them check if you did it right.

so basically what you are saying is that if he doesnt know already then he doesnt know enought to know. If this is the way you answer technial questions I wouldnt bother.

If you don't know enough to size a chain properly, you don't know enough about building a bike to do it properly, especially for campy 10-speed stuff. At the very least, take it to a bike shop and have them check if you did it right.
so basically what you are saying is that if he doesnt know already then he doesnt know enought to know. If this is the way you answer technial questions I wouldnt bother.
Don't you know? All bicycle mechanics are born with this knowledge; they've never had to ask such questions.

With 53-39 / 12-25 and a short-cage racing-style derailleur, you may be challenging your rear derailleur's take-up capacity (53+25-39-12=27 teeth). Ideally, you want the chain to be long enough to accommodate a shift into the 53/25 cross (which you solemnly swear never to use) safely and smoothly, but short enough not to sag severely in the 39/12 cross (which of course you also solemnly swear never to use). If you cannot achieve both objectives simultaneously, err towards excessive length, unless you trust yourself NEVER to attempt a large-large crosschain shift.

I use a short-cage SunTour Cyclone II on the PKN-10, whose 48-45-34/13-23 gearing requires the derailleur's full rated 24-tooth wrap capacity. I have just a hint of chain slack in the 34/13 combo, and everything works very smoothly.

so basically what you are saying is that if he doesnt know already then he doesnt know enought to know. If this is the way you answer technial questions I wouldnt bother.

Please don't feed the trolls. Thanks! :)