The Pro-Rata Rule and Roth Conversions: Today’s Slott Report Mailbag

QUESTION:

My wife has two after-tax traditional IRAs at two separate institutions. We are hoping to consolidate them, then convert to a Roth in the next 18 months. She is already retired. She also has an inherited IRA (from her father). Does the calculation for taxation on the conversion to Roth need to include the assets in the inherited IRA? Do assets in my IRA have any impact on the calculation?