Roth Conversion Calculator: How Much to Convert, and Is It Worth It?

A Roth conversion moves money from a traditional IRA or 401(k) to a Roth IRA. The amount converted is taxable income in the year you convert (IRS Publication 590-A), and from then on the money grows tax-free, with no required minimum distributions for you or your spouse. The question is never whether a Roth is better than a traditional IRA in the abstract. It is whether the tax rate you pay to convert this year is lower than the rate the same dollars would face later: as RMDs stacked on Social Security, as a widow's income on single brackets, or in your children's hands.

For most people with large pre-tax savings, the cheapest years are the ones between the last paycheck and the start of Social Security and RMDs. Taxable income can be very low then, often just a small pension and some interest, while the money you live on comes from savings that were taxed long ago. RMDs start at 73, or at 75 for anyone born in 1960 or later (IRS Publication 590-B). Delaying Social Security to 70 widens the window, and it is the reason conversions and delayed claiming so often go together.

Illustrative example: the people and figures below are hypothetical, not real clients. Numbers are calculated from the stated assumptions.

The calculator opens on Richard, 64, and Anne, 62, both retired and filing jointly. They have $1,500,000 in IRAs, $50,000 in Roth accounts and $400,000 in taxable savings, and $20,000 a year of pension and interest. Richard will claim $42,000 of Social Security at 70; Anne claims $24,000 at 67. Born in 1962, Richard faces RMDs from 75.

If they do nothing, the IRA keeps growing until 75, and the first RMD is $93,869. It lands on top of both Social Security benefits, so that year $56,100 of their benefits is taxable, their MAGI is $169,969, and they owe $16,894 of federal tax. The RMD then grows each year as the IRS divisor shrinks. Over the plan to 92, they pay $438,609 in federal tax and IRMAA.

Filling the 22% bracket each year from 64 to 69 converts $1,335,929 in 6 years, at an average cost of 17.1% in federal tax and IRMAA. The first RMD falls to $17,823, and their MAGI at 75 to $66,623. Lifetime tax and IRMAA come to $282,767, and they end the plan +$396,480 better off after tax, with the IRA they leave valued after a 24% rate for their heirs. The cumulative tax they have paid drops below the no-conversion path at 87, which is the break-even the calculator reports.

That last figure deserves a moment. Converting front-loads tax: by 69they have paid far more than they would have. The saving comes back slowly, a few thousand dollars a year in lower tax on smaller RMDs, and much of the advantage at the end is the tax their children will not owe on a smaller inherited IRA. A conversion plan is a long bet on your own longevity and your heirs' tax rates, not a quick win.

There are two common ways to size a conversion. Filling a bracket converts whatever fits under the top of a chosen rate each year. In 2026 the 22% bracket for a joint return ends at $211,400 of taxable income (Revenue Procedure 2025-32); add the $32,200 standard deduction, the extra deduction for each spouse 65 or older, and the senior deduction that runs through 2028, and subtract your other income, and what is left is the room. The amount changes every year as ages, deductions and other income change, which is the point: the rate stays the same. A fixed amount is simpler to plan around and to explain to a custodian, but the rate it pays drifts as your other income rises.

The table runs the example couple through five strategies, each stopping at 69. Every figure is the calculator's, over the plan to 92.

Two things stand out. First, more is not always better. For this couple, the plan that comes out furthest ahead is “Stay at the standard Medicare premium”, at +$402,324. Filling the 24% bracket converts $1,584,628 in a few years, pays 22.0% on average and gains only +$247,560: those dollars would have faced roughly the same rate as RMDs. Conversions pay when the rate now is clearly below the rate later, and the gap is widest at the bottom of the brackets.

Second, the cheap dollars come first. The early, low-rate conversions do most of the work; each extra dollar converted at a higher rate adds less. Run your own figures with two or three strategies before settling on one, and use the tax bracket calculatorto see exactly how much room is left in this year's bracket.

Should conversions continue after Social Security starts?

In the example, conversions stop at 69, the year before Richard's benefit begins. Carrying the same 22% fill on to 74 converts $1,704,897 instead of $1,335,929 and changes the result from +$396,480 to +$401,061. That is a small difference for $368,968 more converted: once benefits are being paid, each converted dollar also makes more of them taxable, which is the torpedo described below, so the later conversions buy less than the early ones.

Medicare Part B and Part D premiums carry an income-related surcharge, IRMAA, based on your modified adjusted gross income from the tax return 2 years earlier. In 2026 the first tier starts above $218,000 on a joint return and $109,000 on a single one (CMS, 2026 Medicare Parts A & B premiums and deductibles). A conversion is MAGI. Because of the lookback, income in the year you turn 63 sets your premiums at 65, so conversions at 63 and later can raise Medicare costs, while conversions before 63 never can. The calculator charges the surcharge to the year whose income causes it, and only for each person who will be 65 by the premium year.

Filling the 22% bracket puts the example couple's MAGI at $243,599 in 2026, above the $218,000 threshold, so 6 of their 6 conversion years carry a surcharge, $12,632in all. The IRMAA-limited strategy, which stops each year's conversion at the threshold, converts $1,167,594, pays $0 of IRMAA over the whole plan and ends at +$402,324. IRMAA is a cliff, not a rate: a dollar over the line costs the whole tier for the year. Sometimes that is worth paying for a larger conversion; check with the IRMAA calculator before you choose a year-end amount.

Without conversions, the same couple pays $6,890 of IRMAA over the plan, in the late years when growing RMDs push MAGI over the threshold. With both of them alive to 92, converting actually pays more IRMAA in total, because the conversions themselves cross the line. What shrinking the IRA buys is protection against larger surcharges later, and it matters most if one of them is widowed and tested against the single thresholds, as the section on the widow's penalty shows.

Up to 85% of Social Security becomes taxable as other income rises. In the range where benefits are being pulled into tax, each extra dollar of IRA income adds itself plus 50 or 85 cents of benefits to taxable income, so the marginal rate is 1.5 or 1.85 times the bracket rate. That is the tax torpedo, and it explains why the years before benefits start are the cheapest years to convert.

The table shows the example couple at 71 and 69, with both benefits ($66,000 a year) and $20,000 of pension and interest, as IRA income (a conversion or an RMD) is added. The last column is the federal tax on the next $1,000, from the same engine the calculator uses.

At $30,000 of IRA income the couple is in the 12% bracket but pays 22.2% on the next dollar. The rate falls back once 85% of benefits is taxable, then rises again as income reaches the 22% bracket and the senior deduction starts to phase out; the peak in this range is 24.6%. The taxable Social Security calculator walks through the IRS worksheet line by line for your own figures. A conversion made before benefits begin avoids the torpedo entirely, and smaller RMDs later keep you out of it, or push you through it into the flat 85% zone.

When one spouse dies, the survivor usually files as single from the following year. Income often falls less than expected: the survivor keeps the larger of the two Social Security benefits, any survivor pension, and the whole IRA, whose RMDs continue. But the single brackets and IRMAA thresholds are roughly half the joint ones, so the same income is taxed harder. Conversions done while both spouses are alive pay tax at joint rates on money the survivor would otherwise draw at single rates.

Illustrative example: the people and figures below are hypothetical, not real clients. Numbers are calculated from the stated assumptions.

Suppose one of the example couple dies when Richard is 80. Without conversions, in the next year the survivor keeps the larger benefit and still takes the RMD, so MAGI falls only from $190,488 to $170,088, yet federal tax rises from $21,950 to $28,992, plus $2,885 of IRMAA on the single thresholds. Over the plan, that path pays $53,705 of IRMAA. With the same 22% conversions, the advantage of converting rises from +$396,480 with both alive to +$515,991. The calculator's survivor input switches the filing status for you; try the age you think realistic, and an earlier one.

Most adult children who inherit an IRA must empty it by the end of the tenth year after the owner's death, and if the owner had already started RMDs, they must also take annual distributions in the meantime (IRS Publication 590-B). A traditional IRA drawn down over ten years on top of a peak-career salary is often taxed at 24% to 35%. An inherited Roth follows the same ten-year deadline, but the withdrawals are tax-free. Spouses and a few other eligible beneficiaries can stretch withdrawals longer.

That makes the heirs' rate the most important assumption in a long conversion plan. The table holds every other input of the example fixed and changes only that rate.

Even left to charity, this plan stays ahead, by +$104,958: lower tax on smaller RMDs and the Roth's untaxed growth carry it on their own. But every point off the heirs' rate takes a large slice off the result. If your children are in high brackets, or live in high-tax states, conversions are partly a gift to them. If a charity will inherit, the IRA left at your death is never taxed at all, so the case has to rest on your own lifetime tax. The inherited IRA RMD calculator shows what your heirs would have to withdraw each year.

You can pay the conversion tax with money from a taxable account, or have it withheld from the conversion so less reaches the Roth. The conventional advice is to pay from outside, and it is right, but for reasons that are easy to miss.

The reason is growth. Money in the Roth grows untaxed for the rest of your life and your heirs' ten years. Money left in a taxable account pays tax every year on interest, dividends and realized gains. Paying the conversion tax from savings moves the tax bill out of the account that is taxed and keeps the full conversion in the one that is not. The calculator assumes 15%of the savings' return is lost to tax each year (you can change it).

Illustrative example: the people and figures below are hypothetical, not real clients. Numbers are calculated from the stated assumptions.

Paying from savings leaves the example couple +$396,480 ahead of not converting. Having the tax withheld from the conversion instead leaves them +$304,297 ahead: their Roth ends at $3,299,304 instead of $3,945,698, and their savings at $1,552,173 instead of $997,962. The tax itself is the same either way; the difference of $92,183 is the tax drag the larger savings balance carries for decades. With no tax on savings growth (a 0% setting), the two would come out equal, which shows that the drag is the whole difference.

Two more points favor savings. Under 59½, the withheld amount is an early distribution that can carry the 10% additional tax. And if you think of your conversion as a fixed amount, withholding quietly shrinks the part that reaches the Roth. Paying from savings stops making sense only when the savings are needed for living costs, or raising the cash would mean selling holdings with large gains.

Two separate clocks apply to Roth IRAs (IRS Publication 590-B). The first decides whether earnings come out tax-free: a distribution is qualified once you are 59½ and five tax years have passed since your first contribution or conversion to any Roth IRA. If you already have a Roth, even a small one opened years ago, the clock has run. If you do not, the first conversion starts it on January 1 of the year you convert.

The second applies to each conversion and only matters before 59½: converted amounts withdrawn within five years are subject to the 10% additional tax. For a reader converting at 62 or 68 it does not apply, and the amount you converted can always be withdrawn without income tax, because you already paid it.

Until 2017 you could recharacterize a conversion, reversing it by the tax-filing deadline if markets fell or the tax was larger than expected. The Tax Cuts and Jobs Act ended that for conversions made in 2018 and later (IRS Publication 590-A). Every conversion is now final the day it is made.

That has practical consequences. Convert late in the year, when you can estimate the year's income, capital gain distributions and IRMAA position closely, or split the year's amount into two or three pieces. Leave a margin under any bracket or IRMAA threshold you are aiming for. The mechanics of moving the money, by direct transfer or within 60 days, are on the IRS page on rollovers of retirement plan and IRA distributions.

If you retire before Medicare and buy cover on the Marketplace, your premium tax credit depends on household income, and a conversion counts (HealthCare.gov). Credits shrink as income rises and, depending on the rules in force for the year, can stop altogether above 400% of the federal poverty level. A conversion that saves a few thousand dollars of future tax can cost more than that in lost credits. The calculator does not model premium credits, so for the years before 65 check the subsidy at your planned income before converting, or keep conversions small until Medicare starts and the question falls away.

From 70½ you can send up to $111,000 a year (2026) straight from an IRA to charity as a qualified charitable distribution. It never enters income, it counts toward your RMD once RMDs start, and it lowers MAGI for IRMAA and the Social Security worksheet (IRS Publication 590-B). If you give regularly, every dollar you will give through QCDs is a dollar there is no point converting first. Leave enough in the traditional IRA to fund your giving, and convert the rest. Our guide to qualified charitable distributions covers the rules.

The calculator counts federal tax and IRMAA only. Most states tax conversions as ordinary income, and in a state with a 5% rate, this year's $223,599 conversion in the example would add about $11,180. Where you will live matters as much as the rate: converting in a high-tax state the year before you move to one without an income tax pays state tax you could have avoided, and the reverse move makes conversions now more attractive. Some states exempt part of retirement income, and a few treat conversions differently from distributions, so check your own state's rules. Our guide to taxes in retirement covers the main state approaches.

The calculator will show a negative result, or a fragile one, in these situations:

• Your rate later will be lower than now. If RMDs and Social Security will leave you in the 12% bracket, converting at 22% or 24% loses money. The strategy table above shows how quickly larger conversions stop paying.
• A charity will inherit the IRA.The heirs' rate falls to 0%, which removes the largest part of the case: for the example couple the advantage falls from +$396,480 to +$104,958.
• You would have to pay the tax from the IRA before 59½, or the money to pay it would come from selling assets with large gains.
• You need the Marketplace subsidy in the years before Medicare.
• You plan to move to a lower-tax state soon. Wait until you have moved.
• The horizon is short and the heirs' rate is low.If the plan ended at 80, the example couple's cumulative tax never catches up, and the +$184,569 result rests on the 24% rate assumed for their heirs and on the tax drag on savings.

This page is about sizing conversions year by year. For the wider strategy, sequencing conversions with withdrawals and Social Security, read our guide to Roth conversions before RMDs. The RMD calculator projects the distributions you would face without conversions, and the Roth IRA calculator checks whether you can still contribute directly.