Roth Conversion Pro Tool
Advanced simulation engine for optimizing retirement tax brackets, navigating Medicare IRMAA, and avoiding the Social Security Tax Torpedo.
Person 1 (Primary)
Person 2 (Spouse)
Assets, Expenses & Additional Income
Strategy Settings
Note: This rate acts as a marginal proxy applied strictly to the converted dollar amount. It does not calculate your total state tax bill or state-specific Social Security exemptions.
Market Assumptions (%)
Save & Load Scenarios
Save your inputs to a file on your computer to easily compare different strategies later. Your financial data remains 100% private and never leaves your device.
The Ultimate Guide to Roth Conversions & Tax Optimization
Strategically shifting money from a Tax-Deferred account (like a Traditional IRA or 401k) into a Tax-Free account (a Roth IRA) is one of the premier wealth preservation strategies available to retirees today. However, knowing exactly how much to convert without accidentally triggering punitive taxes requires precise mathematical modeling. The Roth Conversion Pro Tool is designed to remove the guesswork from your retirement planning.
Nick leverages over four decades of experience as a software engineer to build institutional-grade retirement tax simulations. He developed this proprietary tax engine to empower individuals with the same progressive tax modeling and cash flow analytics typically reserved for high-net-worth wealth management firms.
How-To Guide: How to Use the Roth Conversion Pro Tool
Our simulation engine runs a dynamic, year-by-year cash flow and tax loop from 2026 all the way to your inputted life expectancy. To get the most accurate projection of your retirement tax liability and legacy wealth, follow these four simple steps:
- Step 1: Enter Household Demographics & Income: Select whether you file as Single or Married Filing Jointly. Enter your birth year (which automatically sets your SECURE Act 2.0 RMD starting age), your retirement age, and your expected Social Security claiming age.
- Step 2: Input Your Current Portfolio Balances: Enter your Traditional IRA/401(k) balance, existing Roth IRA balance, and Outside Cash/Brokerage savings. If you have an unrealized capital gain in your taxable brokerage account, enter the percentage—our tool will automatically calculate long-term capital gains (LTCG) taxes and Net Investment Income Tax (NIIT) as you spend down those funds.
- Step 3: Choose Your Target Conversion Strategy: Select your Target Bracket from the dropdown (or select AUTO-OPTIMIZE to let our algorithm automatically test every bracket to find the exact strategy that maximizes your ending legacy wealth). Ensure you select "Outside Cash" as your tax payment source for optimal compounding.
- Step 4: Analyze Your Timeline & Worksheets: Click "RUN ROTH PRO ANALYSIS." Review your wealth trajectory chart, and click on any individual Year in the results table to open a line-by-line IRS-style worksheet breakdown showing how your Adjusted Gross Income, Social Security taxability, IRMAA penalties, state taxes, and progressive federal tax brackets were computed for that year.
Understanding Your Calculator Inputs
The Roth Conversion Pro Tool requires several specific financial inputs to accurately model your future wealth. Understanding how the engine treats these variables is key to executing an optimal strategy:
- Outside Cash/Brokerage: This is the liquid cash you hold outside of your retirement wrappers. Our tool assumes you will use this bucket first to pay for your living expenses and to cover the tax bills generated by your Roth conversions. Doing so allows the converted funds inside the Roth IRA to compound 100% tax-free without being drained to pay the IRS.
- Brokerage Unrealized Gain (%): If your Outside Cash is invested in the stock market (e.g., in a standard brokerage account), a portion of those funds is likely pure profit. When you sell those funds to pay for living expenses or conversion taxes, the IRS taxes the profit as a Capital Gain. By entering your estimated profit percentage, our engine automatically calculates those exact Long-Term Capital Gains (LTCG) taxes as your cash drains.
- Target Bracket Strategy: The United States utilizes a progressive tax system. When you select a "Target Bracket" (for example, the 12% bracket), the tool will look at your current salary, Social Security, and other income, and then mathematically convert the exact dollar amount needed from your Pre-Tax IRA to fill up the remaining space inside that specific 12% bracket—stopping immediately before your income spills into the higher 22% zone.
How OBBBA Tax Law Changes Affect Conversions
With the passage of the One Big Beautiful Bill Act (OBBBA) in 2025, several critical elements of the tax code were altered that directly impact retirement and estate planning. The legislation permanently cemented the lower marginal income tax rates previously established by the TCJA, ensuring that retirees can continue to execute Roth conversions without fearing an automatic spike in base bracket rates. However, the bill also introduced new deduction rules that must be carefully modeled:
The OBBBA Senior Deduction: Taxpayers aged 65 and older are now eligible for an additional $6,000 above-the-line deduction. However, this deduction carries a strict phase-out cliff based on your Modified Adjusted Gross Income (MAGI). If you execute a massive Roth conversion that pushes your MAGI over the $75,000 threshold (for single filers) or $150,000 (for married filers), you will actively lose this deduction. Our calculator engine automatically monitors this threshold, phasing out the deduction mathematically within the year-by-year worksheet to ensure your strategy doesn't inadvertently trigger a stealth tax hike.
The Charitable Deduction Floor: For retirees who historically utilized large charitable contributions to offset the income generated by Roth conversions, the OBBBA introduced a new 0.5% AGI floor. This means itemized charitable deductions are now only recognized to the extent they exceed half a percent of your Adjusted Gross Income. When running high-volume conversion scenarios, understanding exactly how much of your charitable giving is disqualified by this new floor is crucial for accurate tax projections.
Why Do We Need a Progressive Tax Engine?
Many basic online retirement calculators use a "Flat Tax Proxy"—meaning if you fall into the 22% bracket, they assume your entire income is taxed at 22%. This is a severe mathematical flaw. The U.S. uses a progressive tax system. When you execute a Roth conversion, your first dollars fill up your Standard Deduction (0% tax), then your 10% bracket, then your 12% bracket, and so on.
Our proprietary engine mathematically builds these "stair steps" dynamically, adjusting the ceiling of every bracket for inflation every single year of the simulation to guarantee precision and help you systematically fill specific tax buckets without spilling over.
Real-World Retirement Scenarios & Conversion Strategies
To understand how strategic Roth conversions can protect your retirement savings, let's explore three practical, real-world case studies modeled by our engine:
Scenario 1: The "Gap Years" Strategy (Ages 65 to 70)
The Situation: John and Mary retire at age 65 with $1.5 million in a Traditional 401(k) and $400,000 in a taxable brokerage account. They plan to delay claiming Social Security until age 70 to maximize their monthly benefits.
The Strategy: During the five-year "gap" between age 65 and 70, their wage income drops to $0. Without conversions, they would be in the lowest tax brackets of their lives. Utilizing our tool, they elect to convert enough IRA funds each year to fill the top of the 12% tax bracket, paying the tax bills using their taxable brokerage cash.
The Result: By shifting roughly $350,000 out of their Traditional IRA at historically low tax rates, they drastically reduce their account balance prior to their Required Minimum Distribution (RMD) age, defusing their future RMD "Tax Bomb" and saving tens of thousands of dollars in cumulative lifetime income tax.
Scenario 2: Protecting Against the "Widow's Tax Trap"
The Situation: Robert (age 68) and Susan (age 66) file Married Filing Jointly and hold $2 million in tax-deferred IRA accounts. They are concerned about the financial burden placed on the surviving spouse later in life.
The Strategy: When one spouse passes away, the surviving partner must eventually file taxes as a "Single" taxpayer. Single tax brackets are roughly half the size of Joint brackets, meaning identical RMD withdrawals will push the surviving spouse into drastically higher tax brackets. They use our Smooth Depletion to RMD Age setting to systematically convert IRA funds while both spouses are alive.
The Result: By paying taxes now under the wider Married Filing Jointly brackets, they build a massive tax-free Roth IRA shield. When Robert passes away at age 85, Susan's RMDs are minimal, and she can withdraw from the Roth IRA completely tax-free without triggering Single-bracket tax spikes.
Scenario 3: The Early Retiree ACA Health Subsidy Tightrope
The Situation: David retires early at age 58 under the FIRE movement. He relies on the Affordable Care Act (ACA) marketplace for health insurance and receives substantial Premium Tax Credit subsidies based on his household income.
The Strategy: David wants to begin converting his Traditional IRA to a Roth IRA, but if his Modified Adjusted Gross Income (MAGI) crosses the 400% Federal Poverty Level (FPL) cliff, he could lose his health insurance subsidies, resulting in an unexpected healthcare bill of over $12,000. He enables our Protect ACA Subsidies (<65) feature.
The Result: Our engine actively monitors David's MAGI and mathematically clamps his annual Roth conversion amount to ensure his total income stays safely below the 400% FPL threshold until he reaches Medicare eligibility at age 65.
Frequently Asked Questions (FAQ)
1. What is a Roth conversion, and how is it taxed?
A Roth conversion is the process of transferring retirement funds from a pre-tax account—such as a Traditional IRA, 401(k), or 403(b)—into an after-tax Roth IRA. The amount converted is added to your gross taxable income for that calendar year and taxed at your ordinary federal and state income tax rates. However, once inside the Roth wrapper, the money grows tax-free forever, and all qualified future withdrawals are 100% tax-free.
2. What are Required Minimum Distributions (RMDs), and at what age do they start?
Under the SECURE Act 2.0, the IRS requires account owners to begin withdrawing a minimum mandatory amount from their Traditional IRAs and 401(k)s starting at age 73 (for individuals born between 1951 and 1959) or age 75 (for individuals born in 1960 or later). Roth IRAs are exempt from RMDs during the original owner's lifetime.
3. How does the "Tax Torpedo" affect Social Security taxation?
The IRS taxes Social Security benefits on a sliding scale (0%, 50%, or 85%) based on your Provisional Income (MAGI + 50% of your Social Security benefits). When you execute a Roth conversion, your Provisional Income increases. In certain income bands, every $1.00 you convert can cause an additional $0.85 of Social Security to become taxable, effectively creating a spike in your marginal tax rate known as the "Tax Torpedo." Our calculator dynamically models Provisional Income to avoid this trap.
4. What is Medicare IRMAA, and why does a two-year lookback matter?
The Income-Related Monthly Adjustment Amount (IRMAA) is a statutory surcharge added to your Medicare Part B and Part D premiums if your MAGI exceeds specific cliff thresholds. Medicare uses a strict two-year lookback—meaning your income in 2026 determines your Medicare premiums in 2028. Our tool automatically checks your lookback income against inflated IRMAA cliffs to ensure conversions don't cause unexpected Medicare penalties.
5. Should I pay the taxes on a Roth conversion using IRA funds?
In almost all mathematical scenarios, no. Paying conversion taxes by withholding money directly from your Traditional IRA reduces the amount of capital that makes it into the Roth IRA to compound tax-free. Furthermore, if you are under age 59½, any IRA funds withheld to pay taxes will be treated as an unqualified distribution and hit with an additional 10% early withdrawal penalty. You should always aim to pay conversion taxes using outside taxable cash.
6. What is the difference between Target Bracket and Smooth Depletion?
When you select a Target Bracket (e.g., Fill 12% Bracket), our engine converts the exact dollar amount needed to push your income up to the statutory ceiling of that tax bracket. When you select Smooth Depletion to RMD Age, the algorithm ignores static bracket ceilings and divides your pre-tax IRA balance evenly across your remaining pre-RMD years, creating a smooth, level tax liability across your early retirement runway.
7. What happens to my Roth IRA when I pass away?
Under current IRS inheritance rules (the SECURE Act 10-year rule), most non-spouse beneficiaries who inherit an IRA must completely empty the account within 10 years. If they inherit a Traditional IRA, those withdrawals are fully taxable and can push your children into peak income tax brackets (up to 37%). If they inherit a Roth IRA, every dollar withdrawn during those 10 years is 100% tax-free federal income.
Retirement Tax Library
Explore our deep-dive guides into retirement taxation, Medicare planning, and Roth conversion strategies to optimize your financial legacy:
The tools, charts, and information provided on RothConversionTool.com are intended strictly for educational, informational, and mathematical simulation purposes only. We are not certified public accountants (CPAs), registered fiduciaries, or licensed financial advisors. The outputs generated by this tool do not constitute personalized financial, tax, or legal advice. The U.S. tax code is highly complex and subject to change. You should always consult with a licensed professional before executing real-world tax strategies, altering your investment portfolio, or processing IRA distributions. Any financial decisions you make based on this tool are solely at your own risk.
© 2026 RothConversionTool.com. All rights reserved.