You have savings in a "traditional" tax-deferred retirement account (like a traditional IRA or a 401(k)) and wonder whether it is worth converting them to Roth, paying the taxes now so as never to pay them again. It is one of the most debated decisions in retirement planning, and the answer depends on a few key numbers. The Roth conversion calculator compares the tax cost you pay today to convert with the future taxes you save thanks to tax-free growth, and tells you the net advantage: so you understand, with your own data, whether converting is a winning move or a mistake.

Is converting to Roth worth it? The key question

The Roth conversion is a classic trade-off between present and future: you pay taxes today on the amount you convert, but in exchange that money grows and is withdrawn in retirement completely tax-free. Worth it or not? The answer revolves around two questions. First: will your tax rate be higher or lower in retirement than today? Second: how long and at what return will the money grow before you withdraw it? If you expect similar or higher rates in the future and have a long horizon, converting tends to be very worthwhile. If instead you think you will drop into a much lower bracket in retirement and have little time ahead, today's cost may not pay off. The calculator translates these intuitions into concrete numbers.

What a Roth conversion is

A Roth conversion is the transfer of money from a tax-deferred retirement account (where contributions were deductible and taxes are paid at withdrawal) to a Roth account (where contributions are already taxed but future withdrawals are tax-free). At the moment of conversion, the transferred amount is added to your taxable income for the year and taxed at the current rate: it is the "price" of the conversion. From then on, however, that money lives in a tax-free world: it grows without annual taxes and, provided the conditions are met, is withdrawn in retirement without paying a cent of taxes, including all the accumulated gains. It is the tool with which many savers "lock in" today's rate on capital that will grow for decades, avoiding the uncertainty of future taxation.

How it works: pay taxes now, grow tax-free

The mechanism is a trade over time. Today: you convert an amount from the traditional account to the Roth and pay income tax on that amount, at the current rate. Ideally you pay this tax with external funds (savings outside the retirement account), so as to convert the entire amount. In the following years: the money in the Roth grows with investment returns, without annual taxes on interest, dividends and capital gains. In retirement: you withdraw the grown capital without paying taxes. The calculator models precisely this comparison: on one side today's tax cost, on the other the taxes you would have paid in the future by withdrawing from the traditional account (where the whole balance is taxable) and which, by converting, you do not pay. The difference is the advantage of the conversion.

The tax cost of the conversion today

The immediate cost of the conversion is simple: the amount converted multiplied by your current tax rate. If you convert 100,000 and your rate is 24%, you pay 24,000 of taxes this year. It is a real outlay and must be planned: it increases your taxable income for the year and could, if the amount is large, push you into a higher bracket or trigger other side effects. This is why the conversion is often done in installments over several years, converting each year an amount that stays within a certain bracket. The calculator shows this cost as a dedicated item, because it is the "ticket price": the figure you must be willing (and able) to pay today. The key is that this cost is lower than the future benefit, and that is precisely what the calculator checks.

Tax-free growth and future taxes saved

The real value of the Roth lies in tax-free growth. In the traditional account, the whole balance — principal plus returns — is taxable at withdrawal: the more the money grows, the more taxes you will pay in the future. By converting to Roth, you eliminate this future taxation. The calculator estimates the future value of the amount (which grows at the expected return over the indicated years) and then the future taxes saved, that is how much you would have paid by withdrawing that balance from the traditional at your expected rate in retirement. Here is the crucial point: the tax applies to the grown amount, not the initial one. If 100,000 becomes 320,000 in twenty years, the future taxes avoided are computed on 320,000. This is why, over long horizons, the benefit of the conversion can far exceed the initial cost.

The net advantage: the number that matters

The main result of the calculator is the net advantage of the conversion: the future taxes saved minus the tax cost paid today. If it is positive, converting saves you taxes overall; if it is negative, you pay more today than you will save tomorrow, and the conversion is not worth it. With the default values — 100,000 converted, 24% today, 22% in retirement, 20 years at 6% — today's cost is 24,000, but the future taxes saved are worth about 70,000, for a net advantage of about 46,000. The conversion, in that case, is very worthwhile. The sign and size of the advantage depend on the rates, the horizon and the return: change these values in the calculator to see how the result shifts and find your situation.

Advantage as the horizon changes

Here is how the net advantage changes by converting 100,000 (24% today, 22% in retirement, 6% return) as the years until withdrawal vary:

The longer the horizon, the more the money grows tax-free and the greater the advantage of the conversion. Time is the Roth's best ally: converting young or in any case with many years ahead enormously amplifies the benefit.

Rate today versus rate in the future

Perhaps the most important variable is the comparison between today's rate and the one expected in retirement. The basic logic: convert when you think you will pay taxes at a lower rate today than you would in the future. If you expect higher rates in retirement (for example because you will have a lot of income, or because you foresee a general tax increase), converting now "locks in" the lower current rate and is very advantageous. If instead you foresee dropping into a lower bracket in retirement (lower income, fewer deductions), you might pay less tax by waiting, and the conversion is worth less. Beware though: thanks to tax-free growth, the conversion can be worth it even at equal rates over long horizons, because the benefit applies to a much larger balance. The calculator shows you the combined effect of rates and time.

Advantage as the rates change

Here is how the net advantage changes by converting 100,000 over 20 years at 6%, as the ratio between the current rate and the future rate varies:

Converting at a low rate today to avoid a high rate tomorrow is the ideal scenario (last row). But even when the future rate is slightly lower (second row), the long horizon makes the conversion worthwhile thanks to tax-free growth.

Paying the taxes with external funds

There is a practical rule that maximizes the benefit of the conversion: pay the conversion tax with external money, that is with savings that do not come from the retirement account. Why is it important? If you pay the tax by withdrawing from the same converted amount, you reduce the capital that enters the Roth and that will grow tax-free — and if you are below a certain age you might also incur penalties on the withdrawal. By paying instead with external funds, you convert the entire amount and maximize the capital that works tax-free for decades. The calculator implicitly assumes this optimal scenario (the whole amount grows in the Roth), which is also the one recommended by advisors. If you do not have external funds to pay the tax, the conversion is still possible but the benefit is lower, and it must be assessed with more care.

Roth and minimum withdrawal requirements

An often underestimated advantage of the conversion concerns minimum withdrawal requirements. Many traditional retirement accounts require, past a certain age, withdrawing a minimum share each year — taxed as income — whether you need it or not. These mandatory withdrawals can push your income (and therefore taxes) upward precisely in the years when you would like to stay in a low bracket. Roth accounts, by their nature, generally do not impose these minimum withdrawals on the owner: you can leave the capital to grow tax-free as long as you want, or pass it to heirs. Converting to Roth therefore not only reduces taxation but also gives you flexibility: you control when and how much to withdraw. It is a benefit the calculator does not quantify in currency, but which should be added to the tax advantage in the decision.

When it is worth converting

There are particularly favorable moments for a Roth conversion. Low-income years: if you have a year with reduced income (early retirement before mandatory withdrawals, a sabbatical, a temporary loss of income), your rate is lower and converting costs less. Down markets: converting when investments are worth less means paying the tax on a depressed amount, and then growing the whole recovery tax-free. A long horizon ahead, which amplifies tax-free growth. The expectation of higher rates in the future, for your income or the tax context. Conversely, it is worth less if you are close to retirement with little growth time, if you foresee a strong income drop, or if you have no external funds to pay the tax. The calculator helps you test your specific scenario.

Convert or not: how to decide

Here is a scheme to orient yourself among the typical situations of the Roth conversion:

There is no answer valid for everyone: it depends on rates, horizon, return and your ability to pay the tax today. The calculator gives you the number; the decision also weighs flexibility and inheritance.

Mistakes and cautions

Some caution in the Roth conversion. First: the converted amount increases the year's taxable income and can push you into a higher bracket or trigger side effects (thresholds, contributions, income-linked benefits): it is often worth converting in installments over several years. Second: in many systems there is a waiting rule (often five years) before you can withdraw the converted amounts tax-free; converting too late relative to the need can create problems. Third: pay the tax with external funds, as seen, to maximize the benefit and avoid penalties. Fourth: the precise rules (rates, thresholds, times, any reversibility) vary greatly by country and change over time. The calculator uses a simplified model (constant-return growth, rate comparison) and is not tax advice: use it to understand the order of magnitude and the factors, but decide with a professional.

How the calculator works

Enter the amount to convert, your current tax rate, the expected rate in retirement, the years until withdrawal and the expected annual return. The calculator returns the net advantage of the conversion, the tax cost you pay today, the future taxes saved and the tax-free future value of the capital, with an assessment. Try different horizons and different rate combinations to see when converting becomes worthwhile. It is the quickest way to turn a complex decision — "do I convert or not?" — into clear numbers to compare, and to understand which levers (time, rates, return) matter most in your case.

The data you need

You need five data. The amount to convert from the traditional account to the Roth. Your current tax rate (the marginal rate that would apply to the converted amount this year). The expected rate in retirement, that is the one at which you would be taxed by withdrawing in the future from the traditional account. The years until withdrawal (how long the money will grow). The expected annual return of the investments. The result is the net advantage of the conversion, with today's cost, the future taxes saved and the future value. Remember it is a simplified estimate: the precise tax rules, the effects on income and the thresholds vary by country and situation, and the return is uncertain. Use the calculator to orient yourself, but confirm the strategy with a tax or retirement advisor.

A worked example

You want to convert 100,000 from a traditional account to the Roth. Your current rate is 24%, the one expected in retirement 22%, the horizon 20 years and the expected return 6%. The tax cost today is 100,000 × 24% = 24,000. In 20 years at 6% the amount grows to 320,714: withdrawing it from the traditional you would have paid 22% = 70,557 of taxes, which by converting you avoid. The net advantage is 70,557 − 24,000 = 46,557: the conversion is very worthwhile. Try reducing the horizon to 5 years: the advantage drops a lot. Or set a future rate of 15%: it could become unfavorable. Time and rates rule.

Frequently asked questions

What is a Roth conversion?

It is the transfer of money from a tax-deferred retirement account (traditional IRA, 401(k)) to a Roth account. You pay taxes on the converted amount today, but then that money grows and is withdrawn in retirement tax-free. It serves to "lock in" today's rate and eliminate future taxation on the grown balance.

When is it worth converting to Roth?

When you expect equal or higher rates in retirement, have a long growth horizon, expect good returns and can pay the tax with external funds. It is ideal in low-income years or down markets (you pay the tax on a depressed amount). It is worth less if you will drop a lot in rate and have little time.

How much does the conversion cost today?

The converted amount multiplied by your current tax rate. On 100,000 at 24% you pay 24,000 of taxes this year, added to taxable income. This is why people often convert in installments over several years, staying within a bracket. The calculator shows this cost as a dedicated item.

How is the net advantage calculated?

Advantage = future taxes saved − tax cost today. The future taxes saved are the future value (amount grown at the return over the years) times the expected rate in retirement. Example: 100,000 at 6% for 20 years = 320,714; taxes at 22% = 70,557; minus 24,000 cost today = 46,557 advantage.

Why is tax-free growth so important?

Because in the traditional the whole grown balance is taxable at withdrawal, while in the Roth it is not. The future tax avoided is computed on the GROWN amount, not the initial one: if 100,000 becomes 320,000, the benefit applies to 320,000. Over long horizons this makes conversion worthwhile even at similar rates.

Better to convert if the future rate is higher or lower?

The basic logic: convert if your rate is lower today than it will be in the future (you lock in the low rate). If you expect higher rates in retirement, the conversion is very advantageous. Beware though: thanks to tax-free growth it can be worth it even at equal or slightly lower rates over long horizons.

Should I pay the tax with account funds or external?

With EXTERNAL funds (savings outside the retirement account). This way you convert the entire amount, which all grows tax-free, and maximize the benefit. Paying from the converted account reduces the capital in the Roth and, if you are below a certain age, risks penalties. The calculator assumes this optimal scenario (whole amount in the Roth).

Does the conversion eliminate minimum withdrawal requirements?

Yes, generally Roth accounts do not impose on the owner the mandatory minimum withdrawals that many traditional accounts require past a certain age. This gives you flexibility (withdraw when you want, or leave to grow/pass to heirs) and avoids mandatory withdrawals inflating taxable income in retirement.

Can I convert everything at once?

You can, but often it is not worth it: converting a large amount in one year can push you into a higher bracket and raise the average rate on the conversion, besides triggering income-linked thresholds. Many convert in installments over several years, each year an amount that stays within a bracket, to pay less tax overall.

Is there a waiting period after the conversion?

In many systems yes: often a five-year rule before you can withdraw the converted amounts tax-free (and age-related constraints). Converting too close to the need to withdraw can create complications. Check the specific rules of your country and plan before proceeding.

Does the calculator work for all countries?

The model (you pay the tax today at the current rate, growth is tax-free, you compare with the future cost) reflects the U.S. Roth system, but the logic of "taxing now instead of later" exists in different forms elsewhere. Rates, thresholds, times and eligibility vary greatly by country: use your values and check the local rules.

What data do I need?

Five: the amount to convert, the current tax rate (marginal on the converted amount), the expected rate in retirement, the years until withdrawal and the expected annual return. The result is the net advantage, the cost today, the future taxes saved and the tax-free future value.

Is the result tax advice?

No. It uses a simplified model (constant-return growth, rate comparison) to give you the order of magnitude and the key factors, but it is not advice. The precise rules, effects on income, thresholds and reversibility vary by country and situation, and the return is uncertain. Always decide with an advisor.

Updated July 2026