Which expression is more polite? "Would you~?" or "Could you~?"

[eggcracker]

I know there are no exact words used for politeness, but I want to know some expressions which sound polite.
And I was taught if I use "Would you~" or "Could you~", sentences will be sound more polite.
But I don't know which expression is more polite. Which is better?

 

[BrunaBC]

Re: Which expression is more polite? "Would you~?" or "Could you~?"

NOT A TEACHER

Both ways show politeness. I would also add - would you mind -. See the examples:

Could you turn down the volume please?
Would you turn down the volume please?
Would you mind turning down the volume?