The two accounts can hold identical investments, so the difference is the tax a brokerage account pays on its dividends each year and on its gain when sold, which a Roth does not pay on qualified withdrawals.
How it works
Enter your age, how much you plan to put in each year and for how many years, and your filing status, state and household income.
The calculator invests the same dollars in two places: a Roth IRA funded through the backdoor, and an ordinary taxable brokerage account.
Each year it taxes the brokerage account’s dividends at your federal and state rates, including the net investment income tax where your income reaches it.
At the horizon it sells the brokerage account, taxes the gain, and compares what is left with the Roth balance.
It assumes a clean backdoor with no other pre-tax IRA money, so the conversion itself adds no tax.
Updated September 2026
Updated for the 2026 tax year. Federal brackets, the net investment income tax thresholds and the IRA contribution limit are the 2026 figures; state brackets are each state’s 2025 schedule.
A worked example
Hypothetical result
Contributed
$188K
To each account
Roth at year 25
$508K
No tax due
Brokerage after tax
$403K
After selling everything
Tax the Roth avoids
$86K
Dividend tax plus tax on the sale
A couple married filing jointly in California, age 40, with $400,000 of household income, putting $7,500 a year into each account for 25 years. Both accounts compound at 7% a year, the tool's default assumption, with the dividend and qualified-share defaults.
Year
Age
Backdoor Roth
Brokerage after tax
Roth ahead by
Brokerage tax to date
5
45
$46,150
$43,637
$2,513
$2,444
10
50
$110,877
$100,179
$10,698
$10,029
15
55
$201,660
$174,330
$27,331
$24,628
20
60
$328,989
$272,504
$56,485
$48,796
25
65
$507,574
$403,355
$104,218
$86,120
In this example the backdoor Roth ends year 25 about $104,218 ahead after tax: $86,120 of tax the brokerage account pays and the Roth does not, plus $18,099 that those tax dollars would have compounded into. “Brokerage after tax” is the account as if sold that year; “Brokerage tax to date” is the dividend tax paid so far plus the tax that sale would trigger.
The calculator
Enter your email and it opens immediately.
We ask so we can share the assumptions and research behind the model, and so a real person can answer questions the numbers raise.
We may follow up by email about this tool. No newsletter enrollment, and you can ask us to delete your address at any time.
The 2026 limit is $7,500 per person, plus a $1,100 catch-up at 50 and older. The calculator caps the amount for your age.
Up to the years compared.
Taxable income after deductions, before any investment income.
More detail
Starts at the years until you turn 65. The brokerage account is sold at the end.
Sets where the net investment income tax begins. Leave blank to use household income.
Your own assumption for a diversified portfolio, applied to both accounts.
The part of the assumed return paid out each year, which the brokerage account is taxed on.
Qualified dividends are taxed at capital gains rates; the rest at ordinary rates.
Hypothetical result
The two accounts over time
What each account would hand you after tax at the end of each year. The brokerage line counts the tax that selling it that year would trigger.
Backdoor Roth
Brokerage, after tax
Year by year
Dollars at the end of each year. Brokerage tax to date is the dividend tax paid so far plus the tax a sale that year would trigger.
Age
Year
Backdoor Roth
Brokerage after tax
Roth ahead by
Brokerage tax to date
This piece is general education, not individual advice.
Nothing here is individual tax, legal, or investment advice, and no outcome shown is certain. Results are hypothetical, vary with each use and over time, and are not a prediction of what any account will realize. Whether a backdoor Roth fits your situation depends on your other IRA balances, income, liquidity, and tax picture. Aspirean Wealth, LLC is an SEC-registered investment adviser; registration does not imply a certain level of skill or training.
Assumptions and limitations
Criteria and methodology. The calculator puts identical dollars into two accounts at the start of each year: a Roth IRA reached through the backdoor, and an ordinary taxable brokerage account holding the same investments. The contribution is capped at the 2026 IRA limit, $7,500, plus the $1,100 catch-up from age 50. It assumes a clean backdoor: no pre-tax money in any traditional, SEP or SIMPLE IRA, so the pro-rata rule adds no tax, and the conversion happens immediately, so there are no earnings to tax when it does. Both accounts compound at the assumed annual return you set. Part of that total is paid out each year as dividends, and in the brokerage account those dividends are taxed that year: the qualified share at the 2026 federal long-term capital gains rates, the rest at the 2026 ordinary brackets, both stacked on your household income; and the whole dividend at your state’s 2025 ordinary schedule, except in a state that taxes only capital gains. On top of that, the 3.8% net investment income tax applies to the part of the dividend above $250,000 of modified adjusted gross income for joint filers, $200,000 for single filers and heads of household, and $125,000 for married couples filing separately. The tax comes out of the account and the rest is reinvested. At the horizon the brokerage account is sold in full and the embedded gain is taxed once, at federal long-term rates, the same surtax and your state’s treatment of long-term capital gains. The Roth balance is counted in full, as a qualified withdrawal; money taken out before age 59 and a half, or within five years of the first Roth contribution, can owe tax and a penalty on earnings, which the calculator does not model. Income, tax law and the tax tables are held constant for the whole comparison, with no inflation adjustment and no step-up in basis at death. The fields under More detail start at these values: years compared, the years until you turn 65 (at least two); modified adjusted gross income, the same as household income; the rate both accounts compound at, 7% a year; the share of each year’s balance paid out as dividends, 2%; the share of those dividends that is qualified, 85%. The last three are the assumed annual return, the dividend yield and the qualified share, and all three are yours to set.
Results vary. Every figure changes with each input you enter, and the same inputs would produce different figures as tax law, contribution limits and markets change. The tax tables are a point in time: the 2026 federal schedules and each state’s 2025 schedule, applied unchanged to every year of the comparison. Results vary with each use and over time.
Investments considered. The calculator does not consider, select or recommend any specific investment, fund or portfolio, and it does not use Aspirean’s portfolios. The assumed annual return is your own assumption, applied to a generic diversified portfolio held identically in both accounts for the whole comparison. Other investments not considered may have similar or superior characteristics.
Hypothetical. The outcomes shown are hypothetical. They do not reflect actual trading or the results of any account, and they are not a prediction of what any household will hold. Real results will differ, possibly by a lot, and the gap between the two accounts depends heavily on how long the money stays invested.
Definitions
Nondeductible contribution
Money put into a traditional IRA without taking a tax deduction. It is already-taxed basis, so converting it to a Roth does not tax it again.
Roth conversion
Moving money from a traditional IRA into a Roth IRA. Any pre-tax portion is taxed as ordinary income in the year of the conversion.
Pro-rata rule
The rule that treats a conversion as drawn proportionally from all your pre-tax and after-tax IRA money combined, measured at the end of the year.
Tax drag
The tax a brokerage account pays each year on dividends and interest, which leaves less to compound.
Net investment income tax
A 3.8% federal surtax on investment income above $250,000 of modified adjusted gross income for joint filers, $200,000 for single filers and heads of household, and $125,000 for married couples filing separately.
Frequently asked questions
What is a backdoor Roth IRA?
It is a two-step route into a Roth IRA for people whose income is above the limit for contributing directly. You make a nondeductible contribution to a traditional IRA, then convert it to a Roth. Conversions have no income limit, so the money reaches the Roth by a side door. Both steps are reported on Form 8606 with your return.
Is a backdoor Roth worth it compared with a taxable brokerage account?
Over long horizons it usually is, provided the conversion is clean. The same investments in a brokerage account pay tax on dividends each year and on the gain when sold; inside a Roth, withdrawn after age 59 and a half and five years, they pay neither. The advantage is small in the early years and widens with time, a higher bracket and a high-tax state. The calculator shows the gap in dollars for your horizon.
How does the pro-rata rule affect a backdoor Roth?
If you hold any pre-tax money in traditional, SEP or SIMPLE IRAs on December 31 of the conversion year, the IRS treats each conversion as coming proportionally from pre-tax and after-tax dollars, so part of it becomes taxable, sometimes most of it. This calculator assumes no such balances. If you have them, rolling them into a workplace 401(k) that accepts rollovers can clear the way; check with your CPA first.
Is the backdoor Roth still allowed in 2026?
Yes. Current law does not prohibit a nondeductible contribution followed by a conversion, and Congress has considered closing the route more than once without doing so. Most practitioners now convert soon after the contribution settles, which keeps any taxable earnings in the IRA small. Rules can change, so confirm the year’s position with your CPA before you start.
How much can I put into a backdoor Roth in 2026?
The backdoor is bounded by the ordinary IRA contribution limit, $7,500 for 2026, plus a $1,100 catch-up at age 50 or older. The limit is per person, so a married couple can each fund one, including a spouse without earnings through a spousal IRA when the couple’s earned income covers both. The calculator caps the annual amount at the limit for your age.
Meet with us
Numbers this size deserve a second set of eyes.
If you hold pre-tax IRA money or your income sits near the Roth limits, the order of the steps matters, and it is worth planning the year before the first contribution goes in.
