What a Roth conversion does to your taxes
A Roth conversion moves money from a traditional IRA into a Roth IRA. You pay income tax on the converted amount now, and in return the money can grow in the Roth IRA without more tax on that growth. This calculator tests one question: is paying tax this year better or worse than paying it when you would otherwise withdraw the money? The answer depends mostly on the rate you pay on the conversion today, the rate you expect in retirement and assumptions only you can make.
How the calculator works
First it finds the extra federal tax this year. Your other income, less the 2026 standard deduction, fills the lower brackets. The conversion is stacked on top and taxed at the brackets it reaches, and the table shows how much of it lands in each bracket. State tax is the rate you enter times the amount.
Then it compares two paths to the day you withdraw the money. If you do not convert, the traditional balance grows and is taxed at the rate you expect in retirement. If you convert, the whole amount grows tax free in the Roth IRA. When the conversion tax comes from other savings, those savings stay invested on the no-conversion path, and their growth is taxed at the rate you enter. When the tax comes out of the converted money, the Roth balance is smaller by that tax, and before age 59½ the calculator also covers the 10% additional tax on the part withdrawn.
A worked example
A single filer has $90,000 of other income and converts $50,000. After the $16,100 standard deduction, taxable income is $73,900, in the 22% bracket. The first $31,800 of the conversion fills the rest of that bracket (up to $105,700) and costs $6,996. The remaining $18,200 is taxed at 24% and costs $4,368. The federal tax is $11,364, or 22.7% of the amount converted. With a 5% state rate, the total tax is $13,864.
Now assume a 6% yearly return, 15 years, a 22% tax rate in retirement and tax paid from other savings whose growth would be taxed at 15%. Converting leaves about $119,800 after tax. Not converting leaves about $123,800. On these assumptions, not converting comes out ahead, and converting would win only if the retirement tax rate were above roughly 25.3%. Change an assumption and the answer can flip, so the page also shows other retirement tax rates.
Rules that matter before you convert
- It is taxable income. The converted amount is included in your gross income for the year of the conversion, except for any part that is a return of non-deductible contributions.
- The 5-year rule. Each conversion has its own 5-year period for the 10% additional tax, starting January 1 of the year you convert. If you are younger than 59½ and take out converted money inside that period, the 10% can apply to the part you included in income, unless an exception applies.
- No income limit. Anyone can convert. The income limits in IRS Publication 590-A apply to Roth IRA contributions, not conversions.
- Medicare premiums. Income-related Medicare premiums (IRMAA) are usually based on your tax return from two years earlier. A large conversion can push you into a higher tier two years later. See Medicare costs and IRMAA brackets.
- Required minimum distributions. You cannot convert the amount you must take out for the year. Take your RMD first (use the RMD calculator), then convert the rest.
- No undo. A conversion made in 2018 or later cannot be recharacterized.
What this calculator leaves out
It counts federal income tax on the extra income only. A conversion also raises your adjusted gross income, which can reduce credits, make more Social Security benefit taxable, change ACA premium subsidies and add the 3.8% net investment income tax for some filers. It uses one flat retirement tax rate, no inflation adjustment and no model of the 5-year rule. Use the result to see which assumptions drive the answer, not as a prediction.
Frequently asked questions
Is a Roth conversion a good idea?
It can be when you expect a higher tax rate later than you pay on the conversion. It can be a poor fit when the rate now is higher than the rate you expect later, or when the extra income would cost you credits, benefits or higher Medicare premiums. This page shows the numbers for your assumptions and does not decide for you.
Should I pay the conversion tax from the converted money?
Paying from other savings keeps the whole amount growing in the Roth IRA. Paying from the converted money shrinks the Roth balance, and before age 59½ the part withheld is generally an early withdrawal that can carry the 10% additional tax. Use the switch in the calculator to compare both.
Can I convert a little each year instead of all at once?
Yes. You can make as many conversions as you like, each taxed in the year you make it. Because the brackets rise in steps, a large conversion can be taxed at higher rates than the same amount spread over several years, which is what the line about room before the next bracket shows. Each conversion starts its own 5-year period.
Official sources
Rules checked on irs.gov on October 14, 2026: Publication 590-A (conversions, required distributions, recharacterization), Publication 590-B (the 5-year period and the 10% additional tax) and Revenue Procedure 2025-32 (2026 brackets and standard deduction). Medicare premium tiers: CMS 2026 premiums fact sheet.
This page gives general information and arithmetic, not tax, investment or legal advice. Talk to a tax professional before you convert.