flush-draw strategy Q

[Guruman]

This has probably been covered before, but I haven't been able to find it, so I'll just ask:

Assume I started with a suited Ace pre-flop (like A2[img]/images/graemlins/heart.gif[/img]): what are the odds that I will hit my flush on the flop or turn?

...aand the application being - given the result, how many limpers must I have in the hand with me in order to make a call profitable if it's given that I'll call one bet to see another card on the flop?

Thx!