Converting money from a Traditional IRA to a Roth IRA can be an effective retirement-planning strategy, but the conversion may create an additional tax bill. The Vanguard Roth Conversion Calculator is designed to give you a quick estimate of the federal and state taxes associated with a Roth conversion so you can better understand the potential cost before making a decision.
Vanguard Roth Conversion Calculator
What Is a Roth Conversion?
A Roth conversion is the process of moving money from a Traditional IRA or another eligible retirement account into a Roth IRA. Unlike a normal Roth IRA contribution, a Roth conversion does not rely on the usual annual Roth contribution limit. However, taxable amounts converted from a Traditional IRA can generally become part of your taxable income for the year.
For example, suppose you have $200,000 in a Traditional IRA and decide to convert $40,000 to a Roth IRA. The $40,000 conversion may increase your taxable income and push some of your income into higher marginal federal tax brackets.
The important point is that moving $40,000 does not necessarily mean you pay one flat percentage on the entire $40,000. Federal income tax uses a progressive bracket system. Different portions of taxable income can be taxed at different rates.
The calculator therefore estimates tax before the conversion and then calculates tax again after adding the conversion amount. The difference between those two estimated federal tax amounts is the additional federal tax caused by the conversion.
How the Vanguard Roth Conversion Calculator Works
The calculator asks for several pieces of information.
1. Filing Status
You can choose:
- Single
- Married Filing Jointly
- Head of Household
Your filing status affects both the standard deduction and the federal tax brackets used by the calculator.
For 2026, the IRS lists a standard deduction of $16,100 for single filers, $32,200 for married couples filing jointly, and $24,150 for heads of household.
Because tax brackets vary according to filing status, selecting the correct status is important.
2. Traditional IRA Balance
Enter the current balance of your Traditional IRA.
This value primarily acts as a validation check within the calculator. The requested Roth conversion cannot be greater than the Traditional IRA balance.
For example, if your Traditional IRA balance is $75,000, you cannot enter a conversion amount of $80,000.
It is important to understand that the balance itself is not directly multiplied by a tax rate in the calculator. The tax estimate is based primarily on the conversion amount and the income information you provide.
3. Roth Conversion Amount
This is the amount you are considering moving from the Traditional IRA into the Roth IRA.
For example:
- Traditional IRA balance: $200,000
- Roth conversion amount: $30,000
The calculator uses the $30,000 as additional income for the tax calculation.
Because larger conversions can increase taxable income, the conversion amount is one of the most important values in the calculation.
4. Current Taxable Income Before Conversion
Enter your income before adding the Roth conversion.
There is an important detail about this calculator: despite the field label “Current Taxable Income Before Conversion,” the calculation subsequently subtracts the applicable standard deduction and any additional deduction you enter.
Therefore, this input functions more like an income amount before the calculator applies its built-in deductions. Users should avoid subtracting the standard deduction a second time before entering the figure.
For accurate results, use a consistent definition of income with the calculator's calculation method.
5. Additional Deduction
The calculator allows you to enter an additional deduction.
This amount is added to the selected filing status's standard deduction.
For example, if a taxpayer filing as single enters:
- Standard deduction: $16,100
- Additional deduction: $4,000
The calculator uses a total deduction of:
$16,100 + $4,000 = $20,100
The tool then uses this total deduction when estimating taxable income.
6. Estimated State Tax Rate
Enter your estimated state income tax rate as a percentage.
The calculator accepts a rate from 0% through 20%.
For example, a 5% state tax rate applied to a $30,000 conversion produces an estimated state tax of:
$30,000 × 5% = $1,500
This is a simplified estimate. Actual state taxation can depend on state-specific brackets, deductions, exemptions, credits, residency rules, and other factors.
2026 Federal Tax Brackets Used by the Calculator
The calculator uses progressive federal income tax brackets for 2026.
For single filers, the calculator uses:
| Tax Rate | Taxable Income Threshold |
|---|---|
| 10% | Up to $12,400 |
| 12% | Over $12,400 to $50,400 |
| 22% | Over $50,400 to $105,700 |
| 24% | Over $105,700 to $201,775 |
| 32% | Over $201,775 to $256,225 |
| 35% | Over $256,225 to $640,600 |
| 37% | Over $640,600 |
For married filing jointly, the corresponding thresholds are:
| Tax Rate | Taxable Income Threshold |
|---|---|
| 10% | Up to $24,800 |
| 12% | Over $24,800 to $100,800 |
| 22% | Over $100,800 to $211,400 |
| 24% | Over $211,400 to $403,550 |
| 32% | Over $403,550 to $512,450 |
| 35% | Over $512,450 to $768,700 |
| 37% | Over $768,700 |
The head-of-household thresholds used by the calculator are $17,700, $67,450, $105,700, $201,750, $256,200, and $640,600 for the successive bracket ceilings. These figures correspond to the IRS's 2026 tax-rate tables.
Why Progressive Tax Brackets Matter for Roth Conversions
One common misunderstanding is thinking that moving into a 24% tax bracket means every dollar of income is taxed at 24%.
That is not how progressive tax brackets work.
Suppose a taxpayer has taxable income that reaches into the 24% bracket. Only the portion of income that falls within that bracket is taxed at 24%. Income in the lower brackets is taxed at the applicable lower rates.
This is particularly important when deciding how much to convert.
A taxpayer may want to convert an amount that fills part of a particular tax bracket without moving too much income into the next bracket. This approach is sometimes called bracket management or tax-bracket optimization.
The calculator helps illustrate this concept by calculating the estimated federal tax both before and after the conversion.
Formula Used for the Taxable Income Estimate
The calculator first determines the total deduction:
Total Deduction = Standard Deduction + Additional Deduction
It then calculates income before conversion:
Income Before Conversion = Current Income − Total Deduction
Because the calculator prevents the result from going below zero, it effectively uses:
Income Before Conversion = max(0, Current Income − Total Deduction)
After adding the Roth conversion:
Income After Conversion = Current Income + Roth Conversion − Total Deduction
Again, the minimum taxable-income result is zero.
This approach gives the calculator a starting point for applying the progressive federal tax brackets.
Formula for Additional Federal Tax
The calculator determines estimated federal income tax before the conversion and estimated federal income tax after the conversion.
The central formula is:
Additional Federal Tax = Federal Tax After Conversion − Federal Tax Before Conversion
The calculator also prevents the additional federal tax result from becoming negative.
This difference is useful because it focuses attention on the incremental federal tax caused by the conversion rather than displaying only the taxpayer's total federal tax bill.
Formula for Estimated State Tax
The calculator uses a straightforward percentage estimate:
Estimated State Tax = Roth Conversion Amount × State Tax Rate ÷ 100
For example, suppose you convert $50,000 and enter a 4% state tax rate:
$50,000 × 4% ÷ 100 = $2,000
The estimated state tax would therefore be $2,000.
This should be considered an estimate rather than a complete state tax calculation.
Formula for Total Additional Tax
The calculator combines estimated federal and state taxes:
Total Additional Tax = Additional Federal Tax + Estimated State Tax
For instance, if the additional federal tax is $7,000 and estimated state tax is $2,000:
$7,000 + $2,000 = $9,000
The estimated total additional tax would be $9,000.
Formula for Effective Tax Rate on the Conversion
The calculator calculates the effective tax rate by dividing total additional tax by the conversion amount:
Effective Tax Rate = Total Additional Tax ÷ Conversion Amount × 100
Suppose:
- Roth conversion = $40,000
- Total additional tax = $8,000
Then:
$8,000 ÷ $40,000 × 100 = 20%
The calculator would show an estimated tax on the conversion of approximately 20.00%.
This is an effective rate for the additional tax estimate. It is not necessarily the same as your marginal federal tax bracket.
Formula for the Amount Remaining After Tax
The final major calculation is the estimated net amount remaining after tax:
Net Conversion = Roth Conversion Amount − Total Additional Tax
For example:
- Conversion amount = $40,000
- Total estimated additional tax = $8,000
Then:
$40,000 − $8,000 = $32,000
The calculator would estimate $32,000 remaining after the calculated additional tax.
This figure should not be interpreted as the exact amount that will appear in your Roth IRA after a conversion. The tax payment itself may be made separately, and using retirement assets to pay the tax can have additional consequences.
How to Use the Vanguard Roth Conversion Calculator
Using the tool is straightforward.
Step 1: Select Your Filing Status
Choose Single, Married Filing Jointly, or Head of Household.
Make sure the selection reflects the filing status you expect to use for the relevant tax year.
Step 2: Enter Your Traditional IRA Balance
Enter the total Traditional IRA balance.
This establishes the maximum amount that can be entered as the proposed conversion in the calculator.
Step 3: Enter Your Conversion Amount
Enter the amount you want to consider converting.
You can experiment with several conversion amounts to compare outcomes.
For example, you could test:
- $10,000
- $20,000
- $30,000
- $40,000
Comparing multiple scenarios can help you understand how increasing the conversion affects estimated taxes.
Step 4: Enter Current Income
Enter the current income amount before adding the Roth conversion.
Remember that the calculator then applies the appropriate standard deduction and any additional deduction.
Step 5: Add Any Additional Deduction
Enter a deduction amount when appropriate for your planning scenario.
Leave the field at zero when you do not want to include an additional deduction.
Step 6: Enter Your Estimated State Tax Rate
Enter your estimated state income tax rate between 0% and 20%.
If you are only interested in the federal portion of the estimate, entering 0% will produce no state tax estimate.
Step 7: Click Calculate
After entering the information, select Calculate.
The calculator provides a detailed estimate showing your income before and after conversion, estimated federal tax before and after conversion, additional federal tax, estimated state tax, total additional tax, effective tax rate, and estimated net conversion.
Roth Conversion Example
Consider a hypothetical single taxpayer with these assumptions:
| Input | Example |
|---|---|
| Filing Status | Single |
| Traditional IRA Balance | $200,000 |
| Roth Conversion | $30,000 |
| Current Income Before Conversion | $80,000 |
| Additional Deduction | $0 |
| State Tax Rate | 5% |
For 2026, the single-filer standard deduction used by the calculator is $16,100.
The estimated income before conversion is:
$80,000 − $16,100 = $63,900
After adding the $30,000 conversion:
$80,000 + $30,000 − $16,100 = $93,900
The calculator then applies the progressive 2026 federal tax brackets to both amounts.
The additional federal tax is the difference between the estimated federal tax after conversion and the estimated federal tax before conversion.
The estimated state tax is:
$30,000 × 5% = $1,500
Finally, the calculator adds the additional federal tax and state tax to estimate the total additional tax.
This example demonstrates why the tax cost of a Roth conversion should not be estimated simply by multiplying the conversion by one federal tax rate. The conversion is layered onto the taxpayer's existing taxable income.
When a Roth Conversion May Be Worth Considering
A Roth conversion can be attractive in certain financial situations, although whether it makes sense depends on individual circumstances.
One possible advantage is the opportunity to pay taxes now in exchange for potentially having future qualified Roth IRA distributions treated differently from taxable Traditional IRA distributions.
Another consideration is future tax rates. A taxpayer who expects to be in a higher tax environment later may explore whether paying some tax today could be advantageous.
Some investors also use Roth conversions as part of a broader retirement-income strategy. Rather than converting an entire Traditional IRA in one year, they may consider smaller conversions over multiple tax years.
A calculator like this can help compare these scenarios.
Why Partial Roth Conversions Can Be Useful
You do not necessarily have to convert the entire Traditional IRA balance at once.
For example, suppose your Traditional IRA is worth $500,000. You could investigate a series of smaller conversions rather than automatically converting the full $500,000.
A smaller conversion may help limit the amount of income exposed to higher marginal tax brackets.
You can use the calculator to compare different scenarios and see how the estimated effective tax rate changes as the conversion amount increases.
Testing multiple scenarios can be particularly valuable near the boundary between tax brackets.
Important Roth Conversion Tax Considerations
The calculator provides an estimate rather than a complete tax return calculation.
The IRS states that a Roth conversion generally results in taxation of untaxed amounts in the Traditional IRA. The conversion is reported using the applicable IRA reporting rules, including Form 8606 where required.
However, actual tax liability can be affected by circumstances that this calculator does not model.
These can include tax credits, other deductions, investment income, Medicare-related effects, alternative minimum tax considerations, state-specific rules, and other sources of income.
The calculator also uses a simplified state-tax calculation rather than reproducing every state's complete tax system.
Another important issue is whether your Traditional IRA contains nondeductible contributions. Not every dollar distributed from an IRA is necessarily taxable under every circumstance. IRA taxation can involve basis and pro-rata rules, so taxpayers with nondeductible IRA contributions should be particularly careful when estimating the taxable portion of a conversion.
Benefits of Using a Roth Conversion Calculator
A Roth conversion calculator can be useful because it allows you to examine the potential tax impact before making a financial decision.
Estimate the Potential Tax Cost
The calculator provides an estimate of both federal and state taxes associated with the conversion.
Compare Conversion Amounts
You can enter different conversion amounts and compare the resulting estimated tax costs.
Understand Your Effective Rate
The effective tax rate helps you see how much of the conversion is estimated to be consumed by additional federal and state taxes.
Estimate the Net Conversion
The calculator provides an estimated amount remaining after the additional estimated tax.
Support Retirement Planning
The results can be used as an initial planning reference when considering whether and how much to convert.
Common Mistakes When Planning a Roth Conversion
One common mistake is assuming that your marginal tax rate applies to the entire conversion. Federal tax is progressive, so the incremental tax depends on where the additional income falls within the brackets.
Another mistake is ignoring state income taxes. A conversion that looks attractive from a federal perspective may have a different result after state taxes are considered.
It is also easy to enter income incorrectly. Because this calculator applies a standard deduction to the income entered, entering an already-deducted taxable-income figure may result in the deduction being applied again.
Finally, taxpayers sometimes focus exclusively on the tax bill and overlook other planning considerations. A Roth conversion can affect more than the immediate federal income-tax calculation.
Frequently Asked Questions
1. What is a Vanguard Roth Conversion Calculator?
The Vanguard Roth Conversion Calculator is a calculator concept designed to estimate the tax consequences of converting money from a Traditional IRA to a Roth IRA. The tool estimates federal tax, state tax, total additional tax, effective tax rate, and estimated net conversion.
2. Is a Roth conversion taxable?
Generally, untaxed amounts converted from a Traditional IRA to a Roth IRA are included in taxable income. The IRS explains that a Roth conversion results in taxation of untaxed amounts in the Traditional IRA.
3. Does the calculator use 2026 tax brackets?
Yes. The calculator code uses 2026 federal income tax brackets for Single, Married Filing Jointly, and Head of Household filers. The IRS has published the 2026 inflation-adjusted brackets and deductions.
4. What is the 2026 standard deduction for a single filer?
The 2026 standard deduction for a single filer is $16,100, according to the IRS.
5. What is the 2026 standard deduction for married filing jointly?
For married couples filing jointly, the 2026 standard deduction is $32,200.
6. What is the 2026 standard deduction for Head of Household?
For 2026, the standard deduction for Head of Household is $24,150.
7. Can I convert my entire Traditional IRA?
A full conversion may be possible, but the tax consequences can be substantial because taxable amounts converted in a single year can significantly increase taxable income. The calculator prevents the conversion amount from exceeding the Traditional IRA balance.
8. Should I convert my IRA all at once?
Not necessarily. Some taxpayers consider partial conversions over multiple years to manage the amount of additional income created in each tax year. The appropriate approach depends on your tax situation and financial goals.
9. What does “additional federal tax” mean?
It represents the difference between the calculator's estimated federal income tax after the Roth conversion and its estimated federal income tax before the conversion.
10. What does the effective tax rate mean?
The effective tax rate shown by this calculator is the estimated total additional tax divided by the Roth conversion amount. It includes the calculator's estimated additional federal and state tax.
11. Does the calculator include state taxes?
Yes. You can enter an estimated state tax rate between 0% and 20%. The calculator applies that rate directly to the conversion amount.
12. Does the calculator include every tax deduction and credit?
No. It uses the standard deduction associated with the selected filing status plus the additional deduction you enter. It does not model every possible tax deduction, credit, phaseout, or special tax rule.
13. Does a Roth conversion count as a Roth IRA contribution?
A Roth conversion is different from making a regular annual Roth IRA contribution. A conversion moves eligible retirement assets into a Roth IRA and is subject to different rules.
14. Can the calculator determine my exact tax bill?
No. It is an estimate based on the information entered and the assumptions built into the calculator. Your actual tax liability can differ because of other income, deductions, credits, IRA basis, investment income, state rules, and other factors.
15. Should I consult a tax professional before converting an IRA?
For a significant Roth conversion, professional tax or financial advice can be valuable. A qualified adviser can evaluate factors that a simplified calculator cannot fully model, including your complete tax return, IRA basis, future income, state rules, and other retirement-planning considerations.
Final Thoughts
The Vanguard Roth Conversion Calculator provides a practical way to estimate the potential tax impact of converting money from a Traditional IRA to a Roth IRA. By entering your filing status, IRA balance, conversion amount, current income, additional deduction, and state tax rate, you can see how the proposed conversion may affect estimated federal and state taxes.
The calculator's most useful feature is its comparison of tax before and after the conversion. Rather than assuming that the entire conversion is taxed at one rate, it uses progressive 2026 federal tax brackets to estimate the incremental federal tax created by the conversion. The IRS confirms the 2026 standard deductions and tax brackets used for these calculations.
A Roth conversion can be an important part of long-term retirement planning, but the decision should not be based solely on one estimated tax number. Consider your current income, future tax expectations, retirement timeline, other sources of income, state taxes, IRA basis, and broader financial objectives.
Use the calculator to compare different conversion amounts and understand the potential tax cost. Then use the results as a starting point for more detailed retirement and tax planning rather than treating them as an exact tax-return calculation.