Roth IRA Conversion Calculator

Use the form below to see whether a Roth IRA conversion could improve your long-term after-tax outcome. Enter the conversion amount, your ages, the tax rates, the expected return, and how you plan to pay the conversion tax so the calculator can compare the tax due now with the value of tax-free growth later.

Roth conversion decisions are sensitive to bracket placement, future withdrawal taxes, investment returns, and the number of years the money has to compound. Run a conservative case and a more optimistic case, then compare the results before deciding whether to convert all at once, move money in smaller pieces, or wait for a better tax year.

How to use: Comparing a Roth IRA conversion from start to finish

The quickest way to read this Roth IRA conversion calculator is to focus on the direction of the result after you enter a conversion amount, your ages, the tax rates, and the payment source. A positive net benefit means the Roth conversion is favored under the assumptions you chose; a negative result means keeping the money in the Traditional IRA leaves more value after taxes. Because the model compares a current tax bill with future tax-free growth, even a modest change in bracket, return rate, or payment source can change the outcome.

Start with the conversion amount you are actually considering, then set the current marginal rate and the expected retirement rate as carefully as you can. The calculator lets you test whether the conversion looks better if you do it all at once, in smaller pieces, or not at all, and it shows how the Roth balance changes when the tax bill comes from outside cash versus from the converted dollars themselves.

If you are comparing several Roth conversion ideas, rerun the form for each one instead of trying to blend them mentally. That makes it easier to see whether a year with bonuses, capital gains, self-employment income, or a large distribution has made the conversion less attractive, or whether a lighter-income year has created room to convert more without straining the bracket.

A Roth conversion changes the timing of taxation immediately. The amount you convert becomes taxable now, but future qualified Roth withdrawals can be tax-free, which is why the calculator compares the tax paid today with the after-tax value of leaving the same dollars in the Traditional IRA and letting them compound under the rates you entered.

The payment source matters because it changes how much money begins compounding inside the Roth. If the tax comes from outside retirement funds, the full converted amount stays invested in the Roth. If the tax is withheld from the conversion itself, the Roth starts smaller, and the lost principal can be meaningful over a long retirement horizon.

Roth conversion inputs that change the result

The current marginal tax rate controls the cost of moving the money into the Roth this year. The expected retirement tax rate estimates the tax you would owe later if you kept the money in a Traditional IRA and withdrew it in retirement. A Roth conversion is easier to defend when today’s rate is lower than the rate you expect to face later, when you have many years of compounding ahead, or when you want to reduce future taxable withdrawals.

The return assumption determines how strongly time magnifies the decision. A higher expected return gives the Roth more tax-free growth, but it also raises the value of the money that would have stayed in the Traditional IRA, so the same starting amount can look better or worse depending on the rate you choose. That is why it helps to test conservative, middle, and optimistic return assumptions rather than relying on a single number.

The age fields define the length of the comparison. Your current age and retirement age set the number of years to retirement, and the life expectancy field extends the projection beyond retirement so you can see whether the Roth advantage keeps building later in life or levels off after the early withdrawal years.

The table below summarizes the levers that matter most for a Roth IRA conversion and the kind of what-if test that usually reveals their effect. Even though the calculator distills everything into one result, each of these inputs represents a different piece of the tax tradeoff, and changing any one of them can tilt the outcome.

Worked Roth conversion example: converting $50,000 and paying the tax from outside funds

For a straightforward Roth conversion example, suppose a 50-year-old converts $50,000, expects retirement withdrawals to be taxed at 22%, and assumes 7% annual growth until age 65. The conversion tax at a 24% current rate is $12,000. If that tax is paid from outside funds, the full $50,000 stays in the Roth. If the tax comes out of the conversion itself, only $38,000 starts compounding tax-free, which changes the long-run comparison immediately.

The same setup also runs all the way to the life expectancy field, which extends the comparison from age 50 to age 90. That means the calculator first looks at 15 years to retirement and then continues for another 25 years beyond the retirement age so you can see how the Roth-versus-Traditional gap behaves over a longer retirement horizon. In a longer horizon, small differences in tax treatment can become much larger because the money has more time to compound.

If the conversion year already has a lot of taxable income, the same $50,000 move can be harder to justify. A bonus, capital gain, self-employment income, or a distribution from another account can raise the current cost of converting, so many households test a smaller amount first or wait for a lower-income year. The calculator is most useful when you compare those alternatives side by side instead of assuming that a single conversion size will fit every year.

Paying the tax from outside funds is often the cleaner comparison because it keeps the Roth balance intact from day one. If you need to withhold tax from the conversion, the Roth starts smaller and the lost principal has less time to grow. That difference is easy to underestimate when the tax bill looks modest, but it becomes more important as the conversion amount rises.

Roth IRA conversion assumptions and limitations

This Roth IRA conversion calculator is a planning model, not tax advice. It does not attempt to model every rule that can shape the real answer, including pro-rata treatment of mixed IRA balances, state-specific retirement-income rules, Roth distribution clocks, early-withdrawal penalties, future law changes, or the knock-on effects a conversion can have on other parts of your return.

Use the result as a comparison tool rather than a prediction. Before converting, check your expected taxable income for the year, estimate whether the transaction fits your target bracket, confirm how the tax will be paid, and review the plan with a qualified tax professional who can see the whole picture. If you are trying to manage a bracket boundary, it can also help to test a partial conversion before deciding whether a full conversion is worth the extra tax cost.

Because tax law, market returns, and personal circumstances all change over time, the most useful answer is often a range rather than a single number. Rerun the calculator if your income shifts, if you move to a different state, if your retirement date changes, or if you are considering a year-end conversion after new deductions or earnings come into view.

Formula: how the Roth IRA conversion estimate is built

The math behind this Roth IRA conversion calculator compares the converted dollars under two tax treatments and then adjusts for the source of the conversion tax. The model first computes the years to retirement and the years through life expectancy, then projects the balances forward with the growth rate you entered. That gives you a clean way to compare the Roth path with the Traditional IRA path on the same timeline.

In the equation, C is the conversion amount, r is the expected annual return, y is the projection horizon, tcurrent is the current tax rate, tret is the expected retirement tax rate, and rout is the return on cash used to pay the tax when you choose outside funds. The calculator also treats negative year gaps as zero, so the comparison never runs backward if you enter ages that overlap or reverse the normal retirement timeline.

When the net benefit is positive, the Roth conversion is favored under the assumptions you entered. When it is negative, the Traditional IRA leaves more value after taxes. Because the estimate is sensitive to the bracket you enter and the number of years compounding can work, it is worth rerunning the form after a raise, a bonus, a change in retirement timing, or a market move that changes your expectations.