A Roth conversion moves money from a traditional, pre-tax IRA into a Roth IRA. You pay income tax on the amount converted today, but every dollar that lands in the Roth grows tax-free and comes out tax-free in retirement — with no required minimum distributions during your lifetime and no tax for heirs who inherit it. This calculator projects exactly how much tax you would pay, how much your Roth balance would grow, and how much wealth you would keep versus never converting at all.
The decision comes down to one question: is your tax rate today higher or lower than your tax rate in retirement? If you expect to pay more later — because of large RMDs, a high-income career, or estate-planning taxes — converting during low-income years (early retirement, between jobs, or before Social Security starts) is usually a powerful move. Slide the inputs and watch the net savings figure move.
How to Use
- Enter your current Traditional IRA Balance. This is the pre-tax money in a traditional IRA, rollover IRA, or after-tax 401(k) that you plan to convert. Do not include Roth IRA money you already hold.
- Set the Annual Conversion Amount. A common strategy is to fill the lower federal brackets (for example, stay inside the 22% or 24% bracket) rather than dumping everything in one year. Start with $100,000 and adjust.
- Choose your Conversion Period. Most experts spread conversions over 3–7 years to keep each year's converted sum from jumping into a higher bracket.
- Type the Tax Rate During Conversion. This is your marginal federal rate on the converted dollars. Add your state rate if your state taxes IRA distributions (most do).
- Set the Future Withdrawal Tax Rate. This is the bracket you expect on traditional IRA withdrawals and required minimum distributions (RMDs) if you never convert. If you expect rates to rise, set this higher than the conversion rate.
- Adjust the Expected Annual Return. 7% is a reasonable long-run blended return; lower it to 5% for a conservative portfolio.
- Pick the Projection Horizon. The longer you let the Roth compound tax-free, the bigger the difference — 30 years is a typical planning window for a 60-year-old converting at 65.
The result card shows the total tax you pay now, the tax-free Roth balance at the horizon, the after-tax value of the remaining traditional IRA, and — most importantly — the Net Lifetime Tax Savings, which already subtracts the conversion tax you pay out of pocket today.
Roth IRA Conversion Calculator: How the Math Works
The engine models two competing plans over the same horizon H (years):
- Convert plan: Each year you move
annualConversiondollars from the traditional IRA to the Roth, payconversionTaxRateon that amount from outside savings (so the full converted sum invests), and let both accounts grow atr. If your annual conversion would exhaust the balance before the end of the conversion period, the engine front-loads the schedule — money lands in the Roth earlier and grows longer. The Roth balance at the end isannualConversion × (1+r) × ((1+r)^H − (1+r)^(H−actualYears)) / r, fully tax-free. The leftover traditional balance is grown and then taxed atfutureTaxRate. - No-convert plan: The entire traditional balance grows untouched for H years at
r, then is taxed atfutureTaxRate.
The net lifetime savings subtracts the conversion tax you pay today from the after-tax ending-balance difference. The key asymmetry: every dollar you convert and pay 24% on today permanently removes that dollar — and all of its future growth — from the 24% tax pile. Over 30 years at 7%, $1 grows to about $7.61, so the future tax avoided on that growth dwarfs the tax paid up front.
Worked example on a $500,000 traditional IRA, converting $100,000 per year for 5 years at a 24% bracket, 7% growth, and a 30-year horizon: you pay about $24,000 per year in conversion tax (roughly $120,000 total), the Roth reaches roughly $3.34 million tax-free, and the net lifetime advantage over never converting is about $327,000 after the $120,000 conversion tax is subtracted. If your future bracket is higher than 24%, the savings grow further.
How to read the savings number honestly: the Net Lifetime Tax Savings already subtracts the conversion tax you pay out of pocket today. It still ignores the investment growth that the conversion tax money would have earned if you had kept it invested in a taxable account. Use the number to compare relative strategies and bracket choices; for a fully netted projection, talk it through with a tax planner.
Examples
Example 1 — The classic 5-year ladder. A 62-year-old retiree with a $500,000 traditional IRA, no pension, and modest part-time income converts $100,000 per year for 5 years while in the 24% bracket. Each conversion costs about $24,000 in tax (paid from a taxable brokerage account, not from the IRA). After 30 years the Roth is worth roughly $3.34 million tax-free, versus roughly $2.89 million after tax if he never converts — a net lifetime savings of about $327,000 after the $120,000 conversion tax, plus no RMDs and tax-free inheritance for the kids.
Example 2 — Large balance, bigger wins. A high-earner age 55 holds $1,000,000 in a rollover IRA and converts $200,000 per year for 5 years at 24%. Total conversion tax is about $240,000, but the Roth balance at a 30-year horizon grows past $6.68 million tax-free. The net lifetime tax savings over doing nothing reach roughly $654,000 after subtracting the $240,000 conversion tax, because converting a larger pile removes more future growth from taxation.
Example 3 — Zero conversion (the no-action baseline). If annualConversion is set to $0, the calculator shows that the convert and no-convert plans are identical — $500,000 growing at 7% for 30 years reaches about $3.8 million, then taxed at 24% leaves about $2.9 million after tax. The net savings reads $0, which is the honest baseline. Slide the conversion amount upward and watch the tax-free Roth slice appear.
Example 4 — Lower future rate (when converting hurts). If your future withdrawal rate is 12% (a low-income retirement) and you convert today at 24%, the net savings figure turns negative — about −$130,000 in the standard $500k / 5-year / 7% scenario. The calculator makes this tradeoff visible: sometimes doing nothing really is the right answer, especially if Congress lowers future brackets.
FAQ
What is a Roth conversion?
A Roth conversion is a reportable transaction where you move all or part of a pre-tax traditional IRA, SEP IRA, SIMPLE IRA, or rollover 401(k) into a Roth IRA. The converted amount is added to your ordinary income for the year and taxed at your marginal rate, but afterward the account grows 100% tax-free and qualified withdrawals are 100% tax-free.
How much tax do I pay on a Roth conversion?
You pay ordinary federal income tax — at your marginal rate — on every dollar converted, plus your state income tax if your state taxes IRA distributions. For a $100,000 conversion in the 24% federal bracket, the bill is $24,000 federally before state tax. This calculator uses your conversionTaxRate input to project the total.
Should I convert my IRA all at once or spread it out?
Spreading it over 3–7 years is usually better. A single large conversion can push you into the 32% or 35% bracket, trigger Medicare IRMAA surcharges, and raise your capital-gains rate. Laddering conversions keeps each year inside your target bracket and lets you react if markets drop or tax law changes.
What is the 5-year rule for Roth conversions?
Each conversion has its own 5-year clock for penalty-free withdrawal of the converted principal (if you are under 59½). Earnings withdrawn before age 59½ and before 5 years may be subject to tax plus a 10% penalty. This calculator models long-horizon tax-free growth and assumes you are past the penalty window; for early conversions, factor in the 5-year rule separately.
Do Roth conversions affect Social Security or Medicare?
Yes. Converted income counts toward your modified adjusted gross income (MAGI), which can (a) make up to 85% of your Social Security benefit taxable, and (b) trigger IRMAA Medicare premium surcharges starting at roughly $103,000 single / $206,000 joint in 2025. Run the conversion through your bracket planner before pulling the trigger in a claiming year.
Can I undo a Roth conversion?
No. Since 2018, the Tax Cuts and Jobs Act eliminated recharacterization (undoing) of Roth conversions. Once the conversion is processed, it is permanent — so size each year's conversion conservatively and over-withhold if needed.
Is a Roth conversion worth it for heirs?
Often yes. Roth IRAs have no lifetime RMDs for the original owner, and heirs who inherit a Roth (under the SECURE Act) generally withdraw it over 10 years with zero income tax. Converting while you are in a low bracket shifts the entire future growth out of your estate's tax pile and leaves a larger, cleaner inheritance.
Disclaimer
This Roth conversion calculator is provided for informational purposes only and does not constitute tax, legal, investment, or financial advice. Projections rely on the inputs you enter and on simplified assumptions about constant returns, constant tax brackets, and no RMD drag; actual outcomes depend on future tax law, market returns, Medicare IRMAA thresholds, Social Security taxation, state taxes, and personal circumstances. Roth conversions are irreversible after processing. Always consult a qualified tax professional or certified financial planner before executing a conversion, especially for amounts over $100,000.