Converting to a Roth in October? What a $300,000 Balance at 60 Could Mean by 75

At 60, a $300,000 traditional IRA gives you about 15 years before the IRS starts forcing withdrawals out of it. Conversions only count for a tax year if they are finished by December 31. That’s why October is when many near-retirees pull out a calculator and ask whether paying tax now beats paying it later.

A poster on r/personalfinance asked the same question. They wrote “I can do about 60K and stay under the IRMAA limit“ (the income level where Medicare premium surcharges begin), but couldn’t tell if converting was worth it. Most people get stuck here: the tax bill arrives today, the return takes years.

• Age: 60, retired or close to it
• Balance: $300,000 pre-tax
• Forced withdrawals begin: age 75 for anyone born in 1960 or later
• Decision: convert some, convert all, or leave it alone

Your Tax Rate Today Versus Your Tax Rate at 75

Every dollar you convert is taxed as ordinary income that year. If your rate is the same now and later, converting changes nothing. The benefit comes from the gap between those two rates.

For 2026, a married couple pays 12% on taxable income up to $100,800, and the 22% bracket runs to $211,400.

Spread the balance evenly over 15 years and you convert about $20,000 a year. That costs roughly $2,400 in the lower bracket and $4,400 in the higher one.

Here’s why that gap matters. Assume a 6% annual return. Left alone, the balance grows to about $719,000 by 75.

The 10-year Treasury currently yields about 5%. Required withdrawals from a pile that size come on top of Social Security, pushing you into a higher bracket in your late 70s than at 61.

Pay the conversion tax with money from outside the IRA if you can. Taking it out of the converted amount leaves fewer dollars growing tax-free, which defeats much of the purpose. A Roth also has no required minimum distributions during the original owner’s lifetime, so the money can keep compounding, and your heirs get income-tax-free distributions.

Three Paths Worth Weighing

1. Fill the low brackets every year. If you’ve stopped working and haven’t started Social Security, your taxable income may be the lowest it will ever be. Converting just enough to fill the 12% or 22% bracket locks in cheap tax. This works best for early retirees with cash outside the IRA.
2. Convert everything at once. A single $300,000 conversion runs through lower brackets into the 24% bracket, which for couples starts above $211,400. You pay higher rates to save tax at rates you might never face.
3. Leave it alone. This makes sense if you’ll spend the money in your 60s, have no outside cash to pay the tax, or expect a lower bracket later.

Medicare and Social Security Costs People Overlook

Medicare sets premiums using income from two years earlier, so a conversion at 63 raises your premiums at 65.

This year, a couple with modified adjusted gross income above $218,000 pays $284 a month each for Part B instead of $203. That’s about $974 extra per person per year.

Social Security adds a second trap. For couples, up to 50% of benefits become taxable once provisional income tops $32,000, and up to 85% once it tops $44,000. If you convert after you start collecting, each converted dollar can also make more of your benefit taxable. That raises your real tax rate on the conversion above the bracket you see on paper.

What to Do Before December

1. Project your taxable income for this year and each year until you claim Social Security. The gap between that number and the top of your current bracket tells you how much you can convert cheaply.
2. Put conversions in ages 60 through 62. Those years come before the Medicare lookback and usually before benefits start, so conversion tax is just the bracket rate with no extra costs.
3. Avoid paying the tax out of the IRA. It reduces the Roth, slows compounding, and turns a reasonable move into a marginal one.

My view: regular conversions fit a retiree with a few low-income years, cash outside the IRA to pay the tax, and a plan to let the money grow or leave it to heirs. Those quiet years between retiring and your first required withdrawal may be the cheapest tax rate you ever see again, and we sized up how to use them in a free Roth guide here. If you’ll need this money within a few years or would have to pay the tax from the account itself, leave the $300,000 where it is.

Contact [email protected] for any questions or corrections.