Roth Conversion Calculator

A Roth conversion calculator compares two after-tax futures: leave money in a traditional IRA and pay ordinary income tax on every withdrawal, or pay tax on the converted amount today and let it grow tax-free. You can run your own numbers with the calculator built into our Roth conversion guide. The output turns on four inputs: current marginal rate, expected retirement rate, assumed return, and time horizon.

What the Calculator Models Well, and What It Misses

Calculators handle the compounding math well. A dollar converted at 22% today that grows for 20 years and is withdrawn at 32% in retirement almost always comes out ahead. A dollar converted at 35% that you plan to spend in five years at 22% almost never does.

What most calculators miss: the secondary effects. Converting $80,000 in one year can push you into a higher Medicare premium tier (IRMAA) two years later, or trigger an ACA premium tax credit clawback if you buy coverage on the exchange, costs that never appear in the basic math.

The Rules, Tradeoffs, and Watchouts

A conversion is a taxable event: the amount converted is added to your ordinary income that year, with no cap on the amount.

A few specifics for 2025. The 22% bracket for a married couple filing jointly runs to roughly $201,050 in taxable income; the 24% bracket extends to $383,900. The years between retirement and RMD age (73 under current law) are often a household's lowest-income years, which makes that window valuable.

Each conversion starts its own 5-year clock. Under 59½, withdrawing converted principal before five years have passed costs a 10% penalty; over 59½, the clock still applies to earnings but not principal.

IRMAA is the watchout most people miss. Medicare premiums are based on your MAGI from two years prior, so a large conversion in 2025 sets your 2027 premiums. The 2025 surcharge tiers start at $106,000 for individuals and $212,000 for couples, and crossing one can add several thousand dollars per year in Medicare costs.

Finally, pay the tax from outside funds. Convert $50,000 and withhold $11,000 for taxes, and you have effectively converted $39,000 while taking a distribution on the withheld amount.

A Worked Example

This is an illustrative example, not a projection for any specific person. A 62-year-old has $1.2M in a traditional IRA, $150,000 in a taxable account, and approximately $40,000 of rental income in 2025, solidly in the 22% bracket.

A basic calculator says she could convert roughly $120,000 before crossing into the 24% bracket, paying around $26,400 in federal tax. What it would not surface: she buys ACA coverage, and that conversion pushes her above the ACA cliff at 400% of the federal poverty level, costing her the premium tax credit and roughly $14,000 in health insurance costs. The true cost is closer to $40,000. A targeted conversion of $40,000 to $50,000, sized to preserve the credit, still cuts her future RMD burden without the hidden cost. The calculator did not give her that answer. The planning did.

How This Connects to the Roth Conversion Pillar

The calculator is a starting point, not a strategy. Which years to convert, how much, which accounts pay the tax, and how to sequence around Social Security and RMDs belong to the framework in Roth Conversion: A Practical Guide for High Earners and Pre-Retirees, which also hosts the calculator itself.

Frequently Asked Questions

Is there a free Roth conversion calculator I can use?

Yes. Our Roth conversion guide includes one, and brokerages such as Fidelity, Vanguard, and Schwab offer them at no cost, though none model your specific income, Medicare, and ACA situation.

Can I convert just part of my traditional IRA?

Yes, any amount in any year, with no minimum. Smaller annual increments, often called a partial conversion strategy, are a common way to fill lower brackets without triggering IRMAA or other income-sensitive thresholds.

Does a Roth conversion count toward my RMD for the year?

No. If you are subject to required minimum distributions, you must take your RMD before converting anything else, and the RMD itself cannot be converted.

Does the 5-year rule reset each year I convert?

Each conversion starts a separate 5-year clock from January 1 of the year it was made, so a 2023 and a 2025 conversion run concurrently. The Roth IRA contribution 5-year rule, which governs tax-free earnings, is different and starts when you first opened any Roth IRA.

What to Do Next

1. Run a basic calculator (Fidelity or Vanguard are reasonable starting points) to get a rough estimate of the tax cost and projected benefit at your expected retirement rate.
2. Map your income for the next three to five years, including Social Security timing, RMD onset, and any ACA or IRMAA exposure, before sizing any single year's conversion.
3. Read the full Roth Conversion guide if you have not already. The bracket math, IRMAA tiers, and sequencing logic are covered there in more depth.
4. If the numbers suggest a meaningful opportunity, a conversation with a fiduciary advisor is worth scheduling before year-end. Conversions cannot be undone after December 31.

The information provided is for educational purposes only and does not constitute investment, legal, or tax advice. Tax law changes frequently — verify current rules before acting. Consult with qualified professionals for guidance specific to your situation.