Electrician, i will be running220 100 amp to a shed in my back yard.?

Question

what size conduit do i need to run i also want some 110 outlets for outdoor lighting

i will be running about 100 feet some conduit will be under house and some barried about 18 inches

Answer 1

One thing missing from your question is the length of cable run. Here is a link to a website where you can download a spreadsheet for sizing. Once you get the calbe size, you can find out the size of the conduit.
Check also with local codes, if you plan to bury it- how deep. As always call your local utiltiy locator before you dig.