Backdoor Roth Calculator: See Your Tax-Free Growth Potential
Use this guide to understand the assumptions, inputs, results, and next steps behind the calculator.
Quick Summary
Determine if a backdoor Roth IRA is the right strategy for you. This calculator shows high-income earners the tax impact of converting, the potential cost of the pro-rata rule, and how much more you could accumulate in a tax-free Roth account compared to a standard taxable brokerage account over time.
This tool is for anyone whose income is too high to contribute directly to a Roth IRA. It helps you quantify the long-term benefits of tax-free growth and withdrawals. If you are also considering converting existing pre-tax funds, our Roth Conversion Calculator can help. For a general comparison of retirement accounts, see our guide on Roth vs. Traditional IRAs.
The results provide a "Backdoor Roth Score" to gauge if this strategy is a good fit, a projection of your Roth balance at retirement, and a direct comparison against a taxable account. You'll see charts illustrating your growing tax-free advantage and a summary of the upfront tax costs versus the long-term tax savings.
How To Use This Calculator
Begin by entering your personal details. Your current age, planned retirement age, annual income (MAGI), and filing status set the foundation for the calculation. The calculator automatically checks if your income exceeds the 2026 Roth IRA contribution limits, which is the primary reason for using the backdoor strategy.
Next, move to the Backdoor Roth Conversion section. Input the amount you plan to contribute annually. The most critical input here is your "Existing Traditional IRA Balance." This field is for any pre-tax money you already have in Traditional, SEP, or SIMPLE IRAs. A balance greater than zero will trigger the pro-rata rule, and the calculator will show you the tax consequences.
Then, adjust the growth assumptions to match your financial plan. The expected annual return will project the growth of your investments, while the tax rate in retirement is used to calculate the after-tax value of a comparable taxable account, highlighting the full benefit of tax-free Roth withdrawals.
Finally, explore the advanced settings to model a "Mega Backdoor Roth" strategy. If your 401(k) plan allows for after-tax contributions and in-service withdrawals or conversions, you can use our After-Tax 401(k) Calculator to see how much extra you can save.
What Each Input Means
Current Age and Retirement Age
These inputs define your investment time horizon. The longer the period between your current age and retirement age, the more time your contributions have to compound tax-free. A longer time horizon typically makes the tax-free growth benefit of a Roth IRA more powerful.
Annual Income (MAGI) and Filing Status
Your Modified Adjusted Gross Income (MAGI) and tax filing status determine your eligibility to contribute directly to a Roth IRA. For 2026, the ability to contribute is phased out for single filers with a MAGI between $150,000 and $165,000, and for married couples filing jointly with a MAGI between $236,000 and $246,000. If your income is above these limits, the backdoor Roth is your only path to a Roth IRA.
Annual Contribution
This is the amount you plan to contribute to a non-deductible Traditional IRA before converting it to a Roth IRA. For 2026, the maximum IRA contribution is $7,000, plus an additional $1,000 catch-up contribution if you are age 50 or older. This calculator automatically caps your contribution at the legal limit.
Existing Traditional IRA Balance
This is the most important input for determining the immediate tax cost of a backdoor Roth. Enter the total balance of all your pre-tax IRAs (Traditional, SEP, SIMPLE). If this amount is greater than zero, the IRS pro-rata rule requires a portion of your conversion to be taxed. To avoid this, many people roll their existing pre-tax IRA balances into their current employer's 401(k) plan before executing the backdoor Roth.
Expected Annual Return and Retirement Tax Rate
Your expected annual return is the average rate of growth you anticipate for your investments. The tax rate in retirement is your estimated effective tax rate on withdrawals from a taxable account during your retirement years. A higher retirement tax rate makes the tax-free nature of Roth withdrawals more valuable. For help estimating future taxes, see our guide on how 401(k) withdrawals are taxed.
Mega Backdoor Roth
This advanced option models an additional savings strategy available to those with a supportive employer 401(k) plan. A mega backdoor Roth involves making after-tax (not Roth) contributions to your 401(k) and then converting that money to a Roth 401(k) or Roth IRA. This allows you to save far more than the standard IRA limits, up to the total 401(k) limit of $70,000 in 2026.
How The Calculator Works
This calculator simulates and compares the long-term outcomes of two investment strategies, starting with the same amount of money.
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The Backdoor Roth IRA Path: It simulates making an annual non-deductible contribution to a Traditional IRA and immediately converting it to a Roth IRA. It first calculates any immediate tax due on the conversion using the pro-rata rule. The full converted amount then grows tax-free inside the Roth IRA until retirement. All withdrawals in retirement are tax-free.
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The Taxable Brokerage Account Path: As a comparison, it simulates investing the same after-tax amount in a standard brokerage account. Each year, it assumes investment growth is taxed at a simplified capital gains rate, creating a "tax drag" that reduces the compounding effect. At retirement, it calculates the tax due on the accumulated gains when the money is withdrawn, using your specified retirement tax rate.
The "Tax-Free Advantage" is the difference between the final, take-home value of the Roth IRA and the final, after-tax value of the taxable brokerage account. This quantifies the net benefit of using the backdoor Roth strategy.
Calculator Formula
The calculations are performed year-by-year to model compounding accurately. Here are the core formulas used.
Pro-Rata Rule and Tax on Conversion
The tax on your conversion depends on your existing pre-tax IRA balances.
pro_rata_percent = existing_traditional_ira_balance / (existing_traditional_ira_balance + annual_contribution)
taxable_portion_of_conversion = annual_contribution * pro_rata_percent
tax_on_conversion = taxable_portion_of_conversion * (marginal_federal_rate + state_rate)
If existing_traditional_ira_balance is $0, the tax_on_conversion is also $0.
Yearly Growth Formulas
The calculator projects the balance of a Backdoor Roth IRA and a comparable taxable account year by year.
Backdoor Roth IRA Growth:
ending_roth_balance = (starting_roth_balance + annual_contribution) * (1 + expected_return)
Taxable Account Growth (Simplified):
investment_growth = starting_taxable_balance * expected_return
tax_drag_on_growth = investment_growth * capital_gains_tax_rate
ending_taxable_balance = starting_taxable_balance + annual_contribution + investment_growth - tax_drag_on_growth
Final Advantage Calculation
At retirement, the calculator determines the final after-tax value of each account.
total_taxable_contributions = annual_contribution * years_of_contributing
taxable_gains_at_retirement = taxable_balance_at_retirement - total_taxable_contributions
tax_on_taxable_withdrawals = taxable_gains_at_retirement * retirement_tax_rate
net_taxable_value = taxable_balance_at_retirement - tax_on_taxable_withdrawals
roth_advantage = roth_balance_at_retirement - net_taxable_value
What Is a Backdoor Roth IRA and Who Is It For?
A backdoor Roth IRA is not an official type of account, but rather a strategy used by high-income earners to fund a Roth IRA. The IRS sets income limits that restrict who can contribute directly to a Roth IRA. The backdoor strategy legally bypasses these limits.
The process involves two steps:
- Contribute: You make a non-deductible contribution to a Traditional IRA. There are no income limits for making non-deductible contributions.
- Convert: Shortly after, you convert the funds from the Traditional IRA to a Roth IRA.
This strategy is designed for individuals and couples whose income exceeds the Roth IRA contribution thresholds. If your income is below the limit, you can and should contribute directly to a Roth IRA without these extra steps. The primary benefit is securing tax-free growth and tax-free withdrawals in retirement, which can be especially valuable if you expect to be in a similar or higher tax bracket in the future.
The Pro-Rata Rule Explained: The Biggest Backdoor Roth Mistake
The pro-rata rule is the most significant pitfall of the backdoor Roth strategy. The IRS requires that when you convert funds from a Traditional IRA to a Roth IRA, the conversion must consist of a proportional (pro-rata) mix of your pre-tax and after-tax IRA dollars.
The IRS views all of your IRAs (Traditional, SEP, SIMPLE) as one single account for this calculation. If you have $95,000 in a pre-tax rollover IRA and you make a new $7,000 non-deductible contribution for a backdoor conversion, your total IRA balance is $102,000. Since 93.1% of that total is pre-tax, 93.1% of your $7,000 conversion ($6,517) will be considered taxable income.
How to Avoid the Pro-Rata Rule: The best way to avoid this tax hit is to have a zero balance in all pre-tax IRA accounts when you do the conversion. Many investors achieve this by rolling over their existing pre-tax IRA funds into their current employer's 401(k) or 403(b) plan, as workplace retirement plans are not included in the pro-rata calculation.
Backdoor Roth vs. Mega Backdoor Roth: What's the Difference?
While they sound similar, the backdoor Roth and mega backdoor Roth are distinct strategies that use different accounts and have different limits.
| Feature | Backdoor Roth IRA | Mega Backdoor Roth |
|---|---|---|
| Account Used | Traditional IRA converted to Roth IRA | After-tax 401(k) converted to Roth 401(k) or Roth IRA |
| Contribution Limit (2026) | $7,000 (+$1,000 if 50+) | Up to the overall 401(k) limit of $70,000, minus employee/employer pre-tax/Roth contributions |
| Requirement | Income above Roth IRA limits | An employer 401(k) plan that allows both after-tax contributions and in-service conversions/withdrawals |
| Pro-Rata Rule | Applies if you have existing pre-tax IRA balances | Does not apply |
The backdoor Roth is a way to get money into a Roth IRA. The mega backdoor Roth is a way to get a much larger amount of money into a Roth account through your 401(k). You can potentially do both in the same year if you are eligible. Use the After-Tax 401(k) Calculator to model the mega backdoor strategy.
Understanding Your Results
Backdoor Roth Score: This score gives you a quick assessment of how well-suited the backdoor Roth strategy is for your situation. A high score indicates you are an ideal candidate (high income, no pro-rata issues, long time horizon).
Summary Cards: These four cards highlight the key numbers: your annual contribution, the immediate tax on conversion (ideally $0), the projected Roth balance at retirement, and the total tax-free advantage over a taxable account.
Pro-Rata Rule Warning: If you have an existing Traditional IRA balance, this section will appear, explaining exactly how much of your conversion is taxable and the resulting tax bill. It serves as a critical alert to address your pre-tax IRA balances before proceeding.
Roth vs. Taxable Growth Chart: This visual shows the power of tax-free compounding. You'll see the Roth IRA balance pull away from the taxable account balance over time, as the taxable account is slowed by the annual "tax drag" on its growth.
Tax Impact Summary: This breaks down the trade-off: the tax you pay now on the conversion versus the tax you save later by avoiding taxes on withdrawals. For a clean backdoor Roth, you pay $0 now and save a significant amount later.
Composition at Retirement: This donut chart shows how much of your final Roth balance came from your direct contributions versus how much came from tax-free investment growth.
Ways To Improve Your Results
If the calculator shows a significant tax on conversion, the most impactful action is to eliminate your pre-tax IRA balances. Contact your 401(k) plan administrator to see if you can roll your existing Traditional IRA funds into your 401(k). This single step can make your backdoor conversion completely tax-free.
To maximize the long-term benefit, contribute the maximum amount allowed each year. For 2026, this is $7,000, or $8,000 if you are age 50 or older.
If you are eligible, explore the mega backdoor Roth strategy through your employer's 401(k). This can dramatically increase your tax-free retirement savings beyond what a regular backdoor Roth can achieve.
Finally, perform the conversion step quickly after making your non-deductible contribution. This minimizes the chance for investment gains to accrue in the Traditional IRA, as any gains would be taxable upon conversion.
Common Mistakes
- Ignoring the Pro-Rata Rule: This is the most costly mistake. Failing to account for existing pre-tax IRA balances can lead to an unexpected tax bill.
- Forgetting to File IRS Form 8606: You must file Form 8606 to report your non-deductible Traditional IRA contributions and your Roth conversion. Failure to do so can result in penalties and complications.
- Investing the Money Before Converting: If you contribute to the Traditional IRA and let it sit for weeks or months, any investment gains will be taxable when you convert. It's best to convert the cash as soon as the funds clear.
- Making a Deductible Contribution: A backdoor Roth requires a non-deductible contribution. If your income is high, you likely aren't eligible for a deduction anyway, but it's crucial to classify the contribution correctly on Form 8606.
- Violating the 5-Year Rule: While contributions can always be withdrawn tax and penalty-free, earnings from a conversion must stay in the account for five years to be withdrawn tax-free before age 59.5. This is an important rule to know for early retirees using a Roth conversion ladder.
Frequently Asked Questions
Quick answers to the questions people usually have after running the retirement calculator.
1Is a backdoor Roth IRA legal?
Yes, the backdoor Roth IRA strategy is completely legal. It is an accepted method acknowledged by the IRS for funding a Roth IRA when your income is too high for direct contributions.
2What is the income limit for a Roth IRA in 2026?
For 2026, the MAGI phase-out range for direct Roth IRA contributions is $150,000 to $165,000 for single filers and $236,000 to $246,000 for those married filing jointly. If your income exceeds the top end of these ranges, you must use the backdoor strategy.
3How do I avoid the pro-rata rule?
To avoid the pro-rata rule, you must have a $0 balance across all of your pre-tax IRA accounts (Traditional, SEP, SIMPLE) on December 31st of the year you make the conversion. The most common way to achieve this is by rolling those IRA balances into your current employer's 401(k) plan.
4What is the difference between a backdoor Roth and a Roth conversion?
A backdoor Roth specifically refers to the two-step process of making a non-deductible contribution and then converting it. A Roth conversion is a more general term for moving funds from any pre-tax retirement account (like a Traditional IRA or 401(k)) to a Roth account, which is typically a taxable event.
5Can I do a backdoor Roth if I have a SEP or SIMPLE IRA?
Yes, but the pre-tax balances in your SEP or SIMPLE IRA will be included in the pro-rata calculation, likely making your conversion taxable. You would need to roll those balances into a 401(k) to avoid the tax.
6When should I do the conversion step?
It is generally best to complete the conversion as soon as possible after the non-deductible contribution settles in your Traditional IRA. This is often called the "step transaction doctrine" and helps minimize any investment gains that could be taxed during the conversion.
7Do I have to do a backdoor Roth every year?
No, you can choose to do a backdoor Roth in any year you are eligible and wish to contribute. Many people make it a regular part of their annual savings plan.
8What is a mega backdoor Roth?
A mega backdoor Roth is a separate strategy that uses after-tax contributions in a 401(k) plan to get much larger amounts of money into a Roth account. It requires a 401(k) plan that specifically allows for both after-tax contributions and in-service distributions or conversions.
9Is a backdoor Roth IRA worth it?
For high-income earners who want to save in a Roth account, it is absolutely worth it. The long-term benefit of tax-free growth and tax-free withdrawals, plus the absence of Required Minimum Distributions (RMDs), is a powerful tool for building wealth. The main consideration is managing the pro-rata rule.
Start Planning Your Tax-Free Future
The backdoor Roth IRA is a powerful strategy for high earners. Use the calculator above to see how it can benefit your retirement plan. Enter your details to understand the tax impact and see your potential tax-free advantage grow over time.
For more tools to optimize your retirement savings, try the Roth IRA Calculator for general projections or the Roth Conversion Calculator to analyze converting existing pre-tax funds. Explore all of our retirement calculators to build a comprehensive financial plan.