As fanfare implies, the relative timing of the conversion and the rollover has no bearing on the calculation of the taxable amount. The calculation is done based on the combined year-end value of all of your traditional IRAs, not the value at any other time during the year. You are required to enter the actual year-end value and only a portion of the conversion will be nontaxable, with the reminder of your basis staying with your traditional IRAs to be applied to future distributions until you have no more funds in traditional IRAs at year-end, at which time all of your remaining basis will have been applied.
