Modeling whether or not a Roth conversion makes sense is quite complex. If you have Social Security income, there can be a range of income where the marginal tax rate is substantially higher than it is at higher incomes, so you might want to test with even higher conversion amounts. You'll want to compare the marginal tax rate on the entire proposed Roth conversion to what your marginal tax rate is expected to be for the last dollars of your RMD since RMDs will be required in future years. If you pay for Medicare Part A or D, you'll also need to take into account IRMAA for the Medicare cost when figuring your marginal tax rate. Also be aware that amounts converted to Roth lower your RMDs for future years and the money grows tax free in the Roth IRA rather than tax deferred (subject to the requirements for qualified distributions), so you could still end up paying less in total taxes over your lifetime than without the Roth conversion despite the higher marginal tax rate now. This assumes that you have the funds to pay the taxes without needing to make a distribution from a retirement account.
