Pot odds formula for flop 1 card to come?

[Popinjay]

I'm looking for an x and y formula to calculate pot odds for on the flop with 1 card to come. x is the number of outs and y is pot odds in the format of y:1. So for example on the flop say you have 8 outs then x would be 8 and y (odds for the turn to hit) would be 4.875.

The same thing with the turn to the river would be nice as well.

Sorry if this is a repost.

Thanks.

y=47/x - 1

For the turn, same thing but one more exposed card:

y=46/x - 1

But this assumes that your opponent is just as likely to be holding some of your outs than two random cards left in the deck