Here are my circumstances: I'm 69yo, single, income from SS & portfolio. I have great cashflow and can easily pay taxes from my cash account. My tIRA is somewhat modest.
I decided that I would do as much Roth conversions as prudent, so as not to drive up my tax rate. I set my minimum IRA distribution amount to my next year's RMD amount. I set a maximum IRA distributions (Roth conversion) to the highest value before New York State taxes my IRA ($20k).
With those parameters and having a pretty good idea of what my taxable investment distrubutions would be, I set out to find the optimum value of a Roth conversion.
I used this tax estimator site:
https://www.dinkytown.net/java/1040-tax-calculator.html#I put in the estimated values of all my taxable income, as well as that RMD value and figured the tax. I started a table showing my AGI, amount of the IRA distribution, and the tax, and the percentage tax bill change from the last increment.
Then I incremented the IRA distribution, by $1000, looking at the amount of increasing taxes. As I went up, more of my SS would be taxed. But when 85% of my SS was taxed the increase in AGI and rate of tax increase dropped back, in my case to 12%.
I kept going until I reached the bend point in the tax rate. With my situation of capital gains having a 0% rate until it wasn't, I saw the bend point from 12% to 27%, showing that my capital gains were at last being taxed at 15%.
My plan is that in December when fund distributions have been made, I will calculate how much of my IRA I can get out of hock with the government.
While I pay more tax this way because I am filling out the brackets, in the long run, either I or my heirs will have to pay tax on my IRA, and capital gains won't be taxed to my heirs. Married couples should take note that upon the death on one spouse, the other loses that deduction in the next year, and the taxes on their IRA can zoom. Those in the ACA should consider not doing this if it ruins the subsidy.
Hope this was helpful.
Dave