If the resulting traditional IRA contribution is nondeductible (or you choose to treat it as nondeductible if it would otherwise be deductible), the $6,500 adds to your basis in nondeductible traditional IRA contributions which factors into the calculation of the taxable amount of your Roth conversions. IF you have other money in traditional IRAs, some portion of your basis will be applied to the Roth conversions and the rest will remain in your traditional IRAs to be applied to future traditional IRA distributions. If you have no other money in traditional IRAs, your entire basis will be applied to your Roth conversions to make that amount of the conversions nontaxable.
The calculations are all done on Form 8606. TurboTax prepares Form 8606 automatically when you enter all of the information for the transactions that you have described here.
