Roth conversion calculator

How the math works

Money in a traditional IRA gets taxed when it comes out. Money in a Roth IRA comes out tax-free, once you meet the rules. A conversion moves money from the first to the second, and the price is that you pay the income tax on it this year instead.

The conversion counts as ordinary income, the same as a paycheck, so it stacks on top of your other income and can push part of it into a higher bracket. The tax shown is your 2026 federal tax with the conversion minus your tax without it, using the 2026 brackets and standard deduction.

Then it follows both paths for the number of years you entered. If you don't convert, the money keeps growing in the traditional IRA, and you pay your retirement tax rate when you take it out. If you convert, it grows in the Roth and comes out tax-free.

How you pay the tax matters a lot:

• From other savings. Converting then works a bit like adding that tax money to the Roth, because its growth is never taxed. In the not-converting path, that same money stays in a regular taxable account, and I tax its growth at 15% when it comes out (a common long-term capital gains rate).
• Out of the converted money. Both paths grow at the same rate, so it comes down to one thing: your tax rate now vs your tax rate later. Converting wins only if today's rate is lower. If you're under 59½, the part kept back for taxes counts as a withdrawal from your IRA, and it generally owes the 10% additional tax on top of the income tax (IRS Topic 557), unless an exception applies. The calculator includes that.

The tax rate in retirement is a guess. Tax laws change, and so does your income, which is why the table shows the same conversion at four different rates. I'd look at the whole table instead of trusting one row.

Before you convert

• You can't undo it. You used to be able to "recharacterize," which basically just means reverse, a conversion back to a traditional IRA. That ended with conversions made in 2018 or later.
• More income this year can cost you in other places. Medicare premiums are based on your income from two years earlier, so a 2026 conversion can raise your 2028 Part B and Part D premiums. That's called IRMAA, the income-related monthly adjustment amount. For 2026 premiums, it kicks in when modified AGI is over $109,000 single or $218,000 married filing jointly. A bigger income can also shrink ACA marketplace premium tax credits. And while the conversion itself isn't investment income, it can push your other investment income (dividends, interest, gains) over the line for the 3.8% net investment income tax.
• Each conversion has its own 5-year clock. If you're under 59½, converted money you take out within 5 years, counting from January 1 of the year you converted, can owe the 10% additional tax. A conversion in 2026 and another in 2027 each get their own clock.
• After-tax money in an IRA changes the math. If you've ever made nondeductible (after-tax) contributions to a traditional IRA, the pro-rata rule decides how much of a conversion is taxable, and this calculator assumes all of it is. The backdoor Roth pro-rata calculator works that part out.

What this leaves out

State income tax, the Medicare, ACA and investment income effects above, credits and deductions that shrink as income rises, and, if you get Social Security, the chance that a conversion makes more of your benefits taxable. It assumes the same return every year (real returns bounce around), and it doesn't count the yearly tax on dividends in the taxable account. It also leaves out one Roth perk: you don't have to take required minimum distributions from a Roth IRA during your lifetime. Married filing separately isn't included.

Watch

• Backdoor Roth IRA Explained (Step by Step Process)