Roth conversion calculator

How this calculator works

A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA. Pre-tax money you convert is added to your taxable income. So the calculator works out your 2026 federal income tax twice, without the conversion and with it, and shows the difference.

Both runs use the 2026 IRS brackets and standard deduction, the extra deduction at 65, the temporary senior deduction and the rules that tax more of your Social Security as income rises. Your age is the age you reach by December 31.

Filling a bracket

Each bracket taxes only the income inside it. In 2026 a single filer pays 12% on taxable income from $12,400 to $50,400, and 22% from there up to $105,700. The calculator shows the top bracket your conversion reaches and how much more fits before the next rate.

That room is counted in dollars converted. Where more of your Social Security is becoming taxable, or the senior deduction is phasing out, each extra dollar converted adds more than a dollar of taxable income, so the room is smaller than the gap to the next bracket.

A worked example

You are single and turn 65 in 2026. You have $50,000 of pension income, $20,000 of Social Security and a $400,000 IRA, and you convert $40,000.

• Without the conversion, $17,000 of your Social Security is taxable, so your income is $67,000. Your deduction is $24,150: $16,100 standard, $2,050 for being 65 and the $6,000 senior deduction. Taxable income is $42,850 and the tax is $4,894.
• With it, your income is $107,000. The senior deduction shrinks by 6% of the income above $75,000, to $4,080. Taxable income is $84,770 and the tax is $13,361.
• The conversion costs about $8,467, or 21.2% of the $40,000. Your top bracket is 22%, and about $19,745 more would fit before 24% starts.

Watch Medicare here. Income of $107,000 is $2,000 under the first 2026 surcharge threshold of $109,000. Convert $2,000 more and your 2028 premiums would rise about $95.70 a month at 2026 rates, or $1,148.40 for the year.

At 5% growth the IRA would hold about $651,558 at the end of 2035 without the conversion, and $586,402 with it. Your first RMD, for 2036 at age 75, drops from about $26,486 to $23,837, and the Roth holds about $65,156. At 2026 brackets, without the senior deduction that ends after 2028, the tax on that RMD falls from about $5,672 to $5,089. An illustration only: future tax law and your income are unknown.

How does a Roth conversion affect Medicare premiums?

Medicare Part B and Part D premiums rise in steps once your income passes set thresholds. This surcharge, IRMAA, looks back two years: your 2026 income sets your 2028 premiums.

In 2026 the standard Part B premium is $202.90 a month, and the first threshold is $109,000 for single filers and $218,000 for joint filers. The income counted is your adjusted gross income plus tax-exempt interest, and one dollar over a threshold moves you up a tier. When the premium year's thresholds are not published yet, the calculator uses the latest ones and says which.

Is a Roth conversion worth it?

No verdict here: the answer depends on numbers nobody has yet. The trade-offs:

• You pay tax now, at rates you know, to shrink RMDs later that will be taxed at rates nobody knows.
• Money in a Roth IRA has no RMDs while you are alive, and qualified withdrawals are tax free.
• A large conversion can reach a higher bracket, make more of your Social Security taxable or raise Medicare premiums two years later. Smaller conversions over several years keep each year's income lower.
• State income tax comes on top, and is not included here.

Can I pay the tax from the IRA itself?

You can, but money held back for tax is a withdrawal, not a conversion. It is taxable income, it never reaches the Roth, and before age 59 and a half it can also owe the 10% additional tax unless an exception applies. Paying from savings outside the IRA keeps the whole conversion in the Roth, which is what the projection assumes.

Can I convert my RMD?

No. An RMD is not eligible for rollover, and the IRS counts a conversion as a rollover from a traditional IRA to a Roth IRA. Once your RMDs have started, you take this year's RMD as well, and it counts as income.

Does a conversion lower my RMDs?

For the account you convert from, yes. Each RMD is the December 31 balance divided by an IRS factor for your age, so a smaller balance means a smaller RMD. RMDs start at 75 for people born in 1960 or later, and at 73 for those born 1951 to 1959 (for 1959, under proposed IRS rules not yet final). The table under the calculator shows both paths.

What this calculator leaves out

• State tax, capital gains, itemized deductions and credits.
• After-tax money in the account: every dollar converted is treated as taxable.
• Your spouse's age on a joint return, so a spouse's extra deductions at 65 are not counted.
• When Roth withdrawals count as qualified, including waiting periods.

The projection assumes the same growth every year and that only RMDs leave the traditional account. Real returns will differ, and so may tax law, brackets and Medicare thresholds.