The Multi-Year Roth Conversion Planner

A Roth conversion moves money from a pre-tax retirement account into a Roth account. The taxable amount adds to income in the conversion year. This tool compares a few ways to spread fully taxable conversions across years before required withdrawals begin. It shows the modeled costs and balances, using the published 2026 tax tables throughout. It does not calculate your lifetime tax bill.

Roth conversion planning is a multi-year trade-off. A single large conversion may increase tax-free compounding but can also push income into higher brackets or IRMAA tiers. Smaller conversions can use lower-rate room across several years, but whether that improves the outcome depends on future tax rates, returns, Medicare enrollment, state rules, and how the conversion tax is funded. This tool compares a few defined strategies; it does not find a universally optimal answer.

Who should use this tool

Readers who want to explore conversions before their own required minimum distributions begin. Use only pre-tax money that would be eligible to convert. An employer plan may restrict when money can move, and an IRA with after-tax contributions needs a separate basis calculation.

The no-conversion baseline simply leaves the money invested for the selected years. It does not withdraw RMDs later. If you already need RMDs, or want a retirement-spending forecast, this tool is not a complete model for that situation.

Walking through the inputs

Starting age, balance and end age. Enter your age and the pre-tax balance you want to model. The schedule includes both the starting age and the ending age. Choose an ending age before your first RMD year; the tool does not determine that year for you or subtract required withdrawals.

Income before the conversion. The ordinary-income field applies until the selected retirement age, then drops to zero. Enter Social Security separately, with its starting age. A pension continuing after retirement needs a more detailed income model than this tool provides. These inputs establish the income that each conversion stacks on top of.

Conversion schedule. Choose a fixed annual amount, a target federal tax bracket, a Medicare surcharge boundary, or no conversions. These are comparison settings, not recommendations. Medicare's income-related surcharge is called IRMAA; the planner uses the published 2026 table as a benchmark, not a prediction of future premiums.

Growth and future tax assumptions. The growth setting applies the same annual rate to both account types; the default is 6%. Tax tables are held at 2026 levels. The future tax-rate setting is a simplified haircut on the ending pre-tax balance, not a calculated future tax bracket. Try different assumptions to see how much they influence the comparison.

How to read the result

The table shows each modeled year's conversion, added tax, Medicare surcharge benchmark and ending balances. Its totals cover only those years. The after-tax comparison values the remaining pre-tax money at your assumed future tax rate and subtracts conversion taxes paid from outside the accounts. It is an ending-balance illustration, not a withdrawal schedule.

A favorable result under one set of assumptions is not a guarantee. Future rates, returns, required withdrawals, state rules and the missed investment growth on money used to pay taxes can change the outcome.

Checks to make before using the result

• Check whether all the money is pre-tax. The planner treats every conversion dollar as taxable. The same owner's Traditional, SEP and SIMPLE IRAs share the IRA basis calculation; a 401(k), Roth IRA or spouse's IRA is not part of that pool.
• Missing the IRMAA two-year look-back. A 2026 tax return generally feeds the 2028 IRMAA determination. Because the 2028 table is not yet published, the planner uses the official 2026 table as a clearly labeled constant-dollar benchmark.
• Forgetting RMD acceleration from inherited IRAs. If you inherited an IRA, your RMD schedule is set by different rules. The planner doesn't model inherited balances — keep them separate.
• Check access to the converted money separately. This tool does not model withdrawals or test five-year conversion clocks. For the tax and potential penalty on taking money out, use the Withdrawal Explainer.
• Planning without state tax. Some states tax the conversion fully, while others exempt some or all of it. The state selector uses simplified rates and rules. New Jersey, Virginia, Maryland, Massachusetts and Colorado are deliberately not modeled: the annual and total outputs exclude state tax and suppress state-sensitive comparisons. New Jersey requires its own IRA basis, graduated-rate, and retirement-exclusion inputs. Virginia applies graduated rates and may reduce an eligible taxpayer’s age deduction as income rises, so taxable conversion income can cost more than a flat-rate shortcut suggests. See the New Jersey guide or Virginia guide and model the state return separately. Georgia is another clear example of the age effect: a flat 4.99% for 2026, but a retirement income exclusion that can take it to zero from age 62 — see the Georgia guide. Maryland also requires county and income-interaction inputs. Read the Maryland guide; state and county tax are not included. Massachusetts also requires its own IRA cost-recovery records and taxable-income inputs for the 5% tax and 4% surtax above the 2026 $1,107,750 threshold. Massachusetts tax is not included. Colorado also requires retirement-income and income-threshold inputs. Read the Colorado guide; Colorado income tax is not included.
• Ohio: a flat 2.75% for 2026 (down from 3.5% in 2024). School districts may add 0–2% depending on the district’s tax base; city income taxes never apply to IRA income — see the Ohio guide.
• North Carolina’s figure reflects the TY2026 flat 3.99% (S.L. 2026-41); the rate falls by statute to 3.49% for 2027–2029 — see the North Carolina guide. Bailey-vested government retirees may owe nothing on a direct conversion.
• Michigan’s 4.25% is correct for TY2026, but this planner does not model the restored retirement subtraction: a converter who has reached 59½ can shelter up to $67,610 (single) or $135,220 (joint) of conversion income, so the figure can overstate the state cost — while a converter under 59½ may owe city tax it does not show. See the Michigan guide.

After you have the schedule

Before acting, confirm the current tax rules, actual income, account basis, required withdrawals and plan restrictions. Revisit the illustration when those facts change. A tax professional can help turn a simplified comparison into a plan that includes your other income and spending needs.

If you're deciding between the Roth 401(k) and Traditional 401(k) at work, the Roth vs. Traditional Comparator answers that separate question.

Worked example: two $40,000 conversions, with the arithmetic shown

Here is a small example you can reproduce. Assume a single filer, age 60, models $200,000 of entirely pre-tax retirement money and no existing Roth balance. Use a zero growth rate to isolate the tax arithmetic, no other income or Social Security, Florida residence, retirement age 60, and a fixed $40,000 conversion for each modeled year. Set the end age to 61: the schedule includes ages 60 and 61, so there are two conversions. Taxes are paid from outside the retirement account.

At the published 2026 single-filer standard deduction of $16,100, each $40,000 conversion leaves $23,900 of taxable income. Federal tax is $1,240 on the first $12,400, plus $1,380 on the next $11,500: $2,620 per conversion. The two conversions total $80,000 and cost $5,240 under these assumptions. Future-year tables are held at 2026 levels here, not predicted.

With no growth or withdrawals, the ending balances are $120,000 pre-tax and $80,000 Roth. At an assumed 22% future tax rate on the remaining pre-tax money, the planner’s comparison is $80,000 + ($120,000 × 78%) − $5,240 = $168,360. With no conversions it is $200,000 × 78% = $156,000. The difference is $12,360 under this simplified comparison.

This is an illustration of tax timing, not a recommendation to convert $40,000. The assumed future tax rate matters, as do investment returns and the opportunity cost of the outside money used to pay tax. Those assumptions can change the result.

No required withdrawals or lifetime tax savings are calculated. This example ends well before the illustrated person’s RMD age. Extending the horizon into RMD years does not make the planner account for those withdrawals or turn this ending-balance comparison into a lifetime forecast.