Roth Conversion Calculator: Is Converting Worth the Tax Bill?
Published 06/09/2026 by
Ante Mazalin
Summary:
A Roth conversion calculator shows whether moving money from a traditional IRA to a Roth pays off after you account for the tax due on the converted amount.
Three factors decide the answer.
- Conversion tax: The converted amount is taxed as ordinary income in the year you convert.
- Future tax rate: Conversion wins when your rate later is higher than the rate you pay to convert now.
- How you pay the tax: Paying the bill from outside funds, not the IRA, is what makes a conversion worthwhile.
A Roth conversion trades a tax bill today for tax-free withdrawals later. Whether that trade is smart depends on your rate now versus your rate in retirement, and on where the tax payment comes from.
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How a Roth conversion works
You move money from a pre-tax traditional IRA into a Roth IRA and pay ordinary income tax on the converted amount that year. After that, the money grows and is withdrawn tax-free.
There is no income limit on conversions, which is what makes the backdoor Roth possible for high earners who cannot contribute to a Roth directly.
The math: what conversion costs and saves
Converting $100,000 triggers tax now at your marginal rate. The table shows the upfront cost, then what that $100,000 becomes after 20 years of 7% growth, tax-free inside the Roth.
| Your bracket at conversion | Tax owed now | Roth value in 20 years | All of it tax-free |
|---|---|---|---|
| 12% | $12,000 | $386,968 | Yes |
| 22% | $22,000 | $386,968 | Yes |
| 24% | $24,000 | $386,968 | Yes |
| 32% | $32,000 | $386,968 | Yes |
The growth is identical in every row, so the only variable is what you pay to convert. Converting at 12% costs $12,000 to free the same $386,968; converting at 32% costs $32,000 for the exact same result.
That is the whole strategy: convert when your rate is low. A year with reduced income, an early-retirement gap before Social Security, or a market dip that shrinks the balance are the prime windows.
Why paying the tax from outside the IRA matters
If you pay the conversion tax out of the IRA itself, you shrink the amount that grows tax-free and, before 59½, may owe a 10% penalty on the withheld portion.
Paying from a separate savings or brokerage account means the full converted balance keeps compounding in the Roth. A conversion that looks marginal on paper often only works when the tax is covered from outside.
How to decide whether to convert
Five checks tell you whether a conversion pays off.
- Compare your current marginal rate to the rate you expect in retirement. Convert when today’s rate is lower.
- Confirm you can pay the tax from outside the IRA, not from the converted balance.
- Size the conversion to fill your current bracket without spilling into the next one (the bracket-fill strategy below).
- Check the five-year clock. Each conversion must sit five years before its earnings can be withdrawn penalty-free.
- Watch knock-on effects: a large conversion can raise Medicare premiums and the taxable share of Social Security.
The bracket-fill strategy
You do not have to convert an entire IRA at once. Converting only enough to reach the top of your current bracket keeps every converted dollar taxed at the lower rate.
For a 2026 single filer, the 22% bracket runs to $103,350 and the 24% bracket to $197,300. If your taxable income is $80,000, converting about $23,000 fills the 22% bracket without tipping any of it into 24%.
Spreading conversions across several lower-income years is how large traditional balances move to Roth without ever paying a top-bracket rate.
Pro Tip: The backdoor Roth is just a conversion. If you earn too much to contribute to a Roth directly, you contribute to a traditional IRA and convert it. The catch is the pro-rata rule: if you hold other pre-tax IRA money, the IRS taxes the conversion proportionally, so the move is cleanest when you have no other traditional IRA balances.
When converting makes sense, and when it doesn’t
Conversion fits savers in a temporarily low bracket, those expecting higher rates later, and anyone who can pay the tax from outside funds and will not touch the money for years.
It makes less sense in three cases:
- You would pay the tax from the IRA. That shrinks the balance and can trigger a penalty, undercutting the benefit.
- Your rate will drop in retirement. Paying a high rate now to avoid a lower one later loses money.
- You need the money within five years. Converted amounts have their own five-year clock before earnings come out penalty-free.
Key takeaways
- A Roth conversion is taxed as ordinary income in the year you convert, with no income limit on who can do it.
- The growth is the same regardless of bracket, so the strategy is simple: convert in low-rate years.
- Pay the conversion tax from outside the IRA, or the math usually stops working.
- Bracket-fill conversions keep every converted dollar in your current bracket; a 2026 single filer can convert up to $103,350 of income at 22%.
- A backdoor Roth is a conversion; the pro-rata rule complicates it if you hold other pre-tax IRA balances.
FAQ
How much tax will I pay on a Roth conversion?
The converted amount is added to your taxable income and taxed at your marginal rate. Converting $100,000 in the 24% bracket costs about $24,000, though part may fall in a lower bracket depending on your other income.
Is a Roth conversion worth it?
It pays off when your tax rate at conversion is lower than your expected rate in retirement, and when you can pay the tax from outside the IRA. It rarely pays off if your future rate will be lower.
What is the five-year rule for conversions?
Each conversion has its own five-year clock. Withdraw the converted amount before five years have passed and before age 59½, and you may owe a 10% penalty on it, even though the conversion tax was already paid.
What is a backdoor Roth IRA?
It is a way for high earners to fund a Roth despite income limits: contribute to a traditional IRA, then convert it to a Roth. The pro-rata rule can create an unexpected tax bill if you hold other pre-tax IRA money.
Can I convert just part of my IRA?
Yes. Partial conversions are common and are the basis of the bracket-fill strategy, where you convert only enough to reach the top of your current tax bracket each year.
Does a Roth conversion affect Medicare or Social Security?
It can. A large conversion raises your income for the year, which can increase Medicare premiums two years later and the taxable portion of Social Security. Spreading conversions out limits the impact.
A conversion ripples through your whole tax picture, not just the IRA. Sense AI, the AI assistant in the SuperMoney app, can help you spot the low-income years where converting costs the least.
If you are still deciding which account to fund in the first place, the Roth vs traditional IRA calculator settles that question, and the Roth IRA calculator projects what the converted balance grows into.
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