How to use this calculator
Enter your age, your pre-tax IRA or 401(k) balance, the income you expect each year before any conversion, and the bracket you are willing to fill. The planner converts as much as fits under that bracket's ceiling each year, year by year, and shows the tax on each one.
Leave the Medicare box ticked to stop each year's conversion just short of an IRMAA threshold. Untick it to see what filling the bracket regardless would cost in surcharges.
Compare the total tax you would pay across the plan against the first required distribution shown at the bottom, which is what happens if you do nothing.
Why conversions are a multi-year decision
A conversion is taxed as ordinary income in the year you make it, so converting a large balance at once pushes that one year through several brackets. Spreading the same balance across several years keeps each year inside a lower bracket, and the difference over a full plan is usually measured in tens of thousands of dollars.
The window that makes this work is the gap between the year you stop earning and the year required minimum distributions start at 73. Income is often at its lowest in those years, which means the widest run of low brackets you will ever have. Once RMDs begin, they fill the low brackets for you and the opportunity narrows.
Filling a bracket, not jumping one
Brackets are marginal: moving into the 24% bracket does not tax all your income at 24%, only the part above the threshold. That is why “filling” a bracket is a real strategy. You convert exactly enough to reach the top of the bracket you have accepted, and not a dollar more.
The planner does that arithmetic each year, accounting for the standard deduction and for any required distribution that has to come out first. An RMD cannot be converted, and it takes up room in your bracket before the conversion does.
The Medicare surcharge nobody plans for
IRMAA is a surcharge on Medicare Part B and Part D premiums that applies once income passes a threshold. It is not a tax on the extra income; it is a step. One dollar over a line costs the entire step for the whole year.
Medicare sets your premium from the tax return you filed two years earlier, so income at 63 sets your premium at 65. A conversion made before 63 never touches it at all, which is the single strongest argument for starting a conversion plan early rather than waiting until Medicare is in sight.
When converting is the wrong move
Conversions are not free, and several situations argue against them:
- You would have to pay the tax out of the IRA itself. Paying from outside money is most of the benefit; paying from inside shrinks the balance that was supposed to grow tax-free.
- Your rate in retirement will be clearly lower than it is now. Then the deduction you already took was worth more than the tax-free growth you would buy.
- You plan to leave the account to charity. A charity pays no income tax on an inherited IRA, so converting pays tax that nobody would ever have owed.
- You are about to apply for financial aid, an ACA subsidy, or anything else means-tested on income. A conversion inflates income for that year.
Frequently asked questions
How many years should I spread a Roth conversion over?
As many as you have between retiring and age 73, usually. The planner defaults to eight years because that is roughly the gap for someone retiring in their mid-60s. More years means smaller annual conversions and a lower bracket on each one; the limit is that RMDs start at 73 and begin filling the low brackets themselves.
Which bracket should I fill to?
Fill to the top of the highest bracket that is still below the rate you expect to pay later, either yourself or through your heirs. For many retirees that is 22% or 24%. If your children are high earners who will inherit the account under the 10-year rule, their rate is the one that matters, and it is often higher than yours.
Will a Roth conversion raise my Medicare premiums?
It can. A conversion raises your modified adjusted gross income for that year, and Medicare reads that return two years later. Converting at 63 or later can therefore raise your premium at 65 or later. Tick the Medicare box to keep each conversion under the threshold, or convert before 63 and avoid the question.
Can I convert my required minimum distribution?
No. An RMD has to be taken and cannot be rolled or converted into a Roth. In any year you owe one, it comes out first and is taxed as income; only what is left in the account above that can be converted. The planner handles this ordering for you.
Should I pay the conversion tax from the IRA?
Usually not. Paying from outside money means the entire converted balance stays invested in the Roth, which is where the benefit comes from. Paying from the IRA shrinks the balance and, if you are under 59 and a half, the money used for tax can also face a penalty.
What does this planner not model?
State income tax, the taxation of Social Security, capital gains stacking, ACA subsidies, and any future change to the brackets. It holds today's federal brackets flat across the whole plan, which is a simplification: the rates are scheduled to change, and that uncertainty is itself an argument for converting while the current rates are known.
Keep reading
- Single-year Roth conversion calculator
- IRMAA calculator: Medicare surcharges in detail
- Family Tax Rate calculator: what your heirs would pay
- Roth IRA conversion strategy: when it helps and when it hurts
- How much should I convert to a Roth IRA?
- Learning Center: retirement accounts
This calculator gives estimates for education only. It is not personalized financial, tax or legal advice. Check your numbers with a qualified professional before you make a decision.