How many mgs of codeine does Oxycontin have?

None.

If, however, you are asking about equivalency, according so several online calculators, 100 mg of codeine (oral) is about equal to 10 mg oxycodone (oral). I can't stress the "about" enough. There is a phenomenon known as Incomplete Cross-conversion. Generally speaking, when someone switches from one opiate to another, they will have a slightly lowertolerance to the new drug than what is indicated by simple conversion.

If you are taking oxy for the first time and have only took codeine in the past, then you have almost no tolerance. Codeine, stated simply, is a weak opiate. You should take less than 10% of the mg's you took of codeine until you see how you react.