Formulas and 2026 figures checked & updated: July 2026
Your marginal tax rate this year.
Your expected marginal tax rate in retirement.
How to Use the Roth Conversion Calculator
- Enter your current Traditional IRA or 401(k) balance.
- Enter the amount you're considering converting to Roth — this can be a partial or full conversion.
- Enter your current age and planned retirement age.
- Set your tax rate now (applied to the conversion) and your expected tax rate at withdrawal.
- Enter your expected annual investment return.
- Compare the after-tax value of converting vs. leaving the balance Traditional.
- Example: converting $50,000 at a 22% tax rate today, when you expect 24% in retirement, still often wins if the money grows tax-free for 15+ years.
What This Calculator Does
The Roth Conversion Calculator projects your Traditional balance forward under two scenarios — converting some or all of it to Roth today, or leaving it untouched — and compares the after-tax value at retirement.
The comparison is driven by six inputs: your current Traditional balance, the amount you're considering converting, your current age, your planned retirement age, and your marginal tax rate now versus your expected marginal tax rate at withdrawal. As a general rule of thumb, a Roth conversion tends to pay off when your current tax rate is lower than or roughly equal to your expected retirement tax rate, since you're effectively locking in today's rate on the converted amount — and the more years the money has to grow before retirement, the more that tax-free compounding advantage compounds too. Many people target conversions during a temporary dip in income, such as a career break, the gap years between retiring and starting Social Security, or a year with unusually large deductions.
This calculator helps with decisions like whether to convert during a low-income year, whether to convert the full amount now versus spread conversions across several years to avoid jumping tax brackets, and whether converting before Required Minimum Distributions begin at age 73 makes sense to reduce future forced withdrawals. It assumes the tax due on conversion is paid from outside savings rather than from the account itself, which is the standard recommendation since it lets the full converted amount keep compounding tax-free.
Formula
Convert Now = FV(converted) + FV(remaining) × (1 − Tax Later) vs. No Convert = FV(full balance) × (1 − Tax Later)FV uses standard compound growth over your years to retirement. The converted portion is untaxed at withdrawal (Roth); the unconverted or non-converted portion is taxed at your assumed retirement rate.
- Tax NowYour marginal tax rate applied to the converted amount this year
- Tax LaterYour expected marginal tax rate when you'd otherwise withdraw
Examples
Example 1: Converting during a lower-income year
$50,000 converted at a 12% rate during a career gap, vs. an expected 24% rate in retirement.
Converting wins clearly — you lock in tax at the lower rate and the full amount grows tax-free afterward.
Example 2: Tax rate expected to drop in retirement
Converting at 24% now, but expecting only 12% in retirement.
Converting usually loses here — you'd pay more tax upfront than you'd have paid later on withdrawal.
Example 3: Converting in stages to stay in a lower bracket
A $50,000 Traditional balance at a 22% current marginal rate — instead of converting the full amount, only $20,000 is converted this year to stay within the 22% bracket, with the remaining $30,000 planned for conversion in future years.
Tax due now is $4,400 versus $11,000 for a full conversion, and the remaining $30,000 keeps growing tax-deferred until converted later — a common strategy sometimes called a Roth conversion ladder, used to avoid pushing income into a higher bracket in any single year.
Key Terms Explained
- Roth IRA
- A retirement account funded with after-tax dollars. Contributions and earnings grow tax-free, and qualified withdrawals in retirement owe no tax.
- Traditional IRA
- A retirement account funded with pre-tax (or deductible) dollars. Contributions may lower your taxable income today, but withdrawals in retirement are taxed as ordinary income.
- Marginal Tax Rate
- The tax rate applied to your last dollar of income — your top tax bracket. It's higher than your effective (average) rate.
- Compound Interest
- Interest earned on both your original balance and previously earned interest, so growth accelerates the longer money stays invested.
- Effective Tax Rate
- Your total tax divided by your total income — the average rate you actually pay across all brackets.
Continue Your Financial Planning
Methodology
Converting: the converted amount grows tax-free as a Roth balance (tax paid from outside funds, assumed not to reduce the converted amount); any remaining Traditional balance keeps growing tax-deferred and is taxed at withdrawal. Not converting: the entire balance stays Traditional, taxed at withdrawal. Both scenarios grow at the same assumed return over the same time horizon.
Frequently Asked Questions
What is a Roth conversion?+
A Roth conversion moves money from a Traditional IRA or 401(k) into a Roth account. You pay ordinary income tax on the converted amount now, in exchange for tax-free growth and tax-free qualified withdrawals later.
When does a Roth conversion make sense?+
Conversions tend to make sense when your current tax rate is lower than you expect it to be in retirement — for example, during a low-income year, early retirement before Social Security starts, or if you expect tax rates to rise.
Should I pay the conversion tax from the account or from savings?+
Paying from outside savings is almost always better — it lets the full converted amount keep growing tax-free in the Roth. Using account funds to pay the tax reduces the amount that grows, and may trigger an early-withdrawal penalty if you're under 59½.
Is there a limit on how much I can convert?+
No — unlike direct Roth contributions, conversions have no income limit or dollar cap. But converting a large amount in one year can push you into a higher tax bracket, so many people convert in smaller chunks over several years.
Do Roth conversions count toward the annual IRA contribution limit?+
No. Roth conversions are separate from annual contribution limits — you can convert any amount from a Traditional account regardless of the yearly IRA contribution cap. However, the converted amount is added to your taxable income for that year and can affect your tax bracket, Medicare premium surcharges (IRMAA), or eligibility for other income-based benefits.
What is a backdoor Roth conversion?+
A backdoor Roth conversion is a strategy where someone whose income is too high to contribute directly to a Roth IRA instead makes a nondeductible contribution to a Traditional IRA and then converts it to a Roth shortly after. Because the contribution was already after-tax, little or no additional tax is typically owed on the conversion, provided the person has no other pre-tax IRA balances that would trigger the pro-rata rule.
How does the 5-year rule affect Roth conversions?+
Each Roth conversion starts its own 5-year clock: converted funds withdrawn within 5 years of that conversion, and before age 59½, can trigger a 10% early-withdrawal penalty on the converted amount even though the conversion itself was already taxed. This is separate from the 5-year rule that applies to Roth IRA earnings, so multiple conversions made in different years each track their own countdown.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.