Assuming you are converting 100% of your IRA dollars, you will pay tax on the total value converted less any basis arising from non deductible contributions to the traditional IRA.
If you are converting LESS THAN 100% of your IRA dollars, then the basis from non deductible contributions has to be allocated between the amount converted and the amount not converted. Form 8606 would handle the workings of the calculation. You can get Roth info at
http://www.rothira.com.
[Edited by BPickerCPA on 09-15-2000 at 09:26 AM]