RetireSmarter
RetireSmarter/Calculators/Roth Conversion Ladder

Roth Conversion Ladder Calculator (2026)

The window between retirement and age 73 is your lowest-tax decade — use it to systematically convert traditional IRA money to Roth while filling brackets and avoiding IRMAA cliffs. This calculator models the Social Security torpedo effect and RMD trajectory to find your optimal conversion amount every year.

Roth Conversion Ladder Planner

Model your optimal annual conversion strategy, accounting for SS taxation and IRMAA cliffs.

Typically 15–25 years

$
$0$3,000,000

Pre-tax retirement accounts subject to RMDs

$
$0$1,000,000

Existing Roth (always accessible)

$
$0$2,000,000

Used to fund living expenses & conversion taxes

6%
1%12%

Applied to all accounts. Conservative: 5–6%; moderate: 7–8%.

$
$0$150,000

Pension, annuity, rental, part-time work

$
$0$60,000
$
$0$60,000
$
$0$50,000

Municipal bonds, etc. Counts toward IRMAA MAGI

Conversions stop when total taxable income reaches this ceiling

$
$20,000$300,000

Total gross annual spending. Covered by income → RMDs → bridge fund

20-Year Projection Summary

Total Roth converted

$934,497

over 5 active years

Total federal tax paid

$165,935

avg $33,187/yr on conversions

Final traditional IRA

$0

from $800,000 today

Final Roth IRA

$2,726,065

from $50,000 today

Final bridge fund

$0

depleted

Projected RMD at age 73

$64,391

if no conversions before 73

Bridge fund depletes before the planning horizon ends. Consider reducing the target bracket, increasing the bridge fund, or shortening the conversion window.

Stacked area shows how Traditional IRA shifts to Roth + bridge fund depletes over time.

This tool uses 2026 federal tax brackets and IRMAA thresholds. All calculations are estimates for planning purposes only — not tax or financial advice. Actual results will vary based on account performance, tax law changes, and individual circumstances. Consult a tax professional before acting.

How a Roth Conversion Ladder Works

A Roth conversion ladder is a multi-year strategy to systematically convert money from your traditional IRA (or 401k) into a Roth IRA — paying ordinary income taxes now, at a controlled rate, to get decades of tax-free growth. The window is the gap between retirement (when your income drops) and age 73 (when RMDs force distributions whether you want them or not).

The core tactic is "bracket filling": convert just enough each year to fill a target tax bracket ceiling — say, the top of the 22% bracket — without crossing into the next bracket. For most retirees, this means converting $50,000–$150,000 per year over a 10–15 year window.

The complications that make this tricky: (1) IRA withdrawals trigger Social Security taxation in a nonlinear way, effectively bumping your marginal rate 50–85% above the statutory rate (the "tax torpedo"). (2) Your MAGI, which includes Roth conversions, determines IRMAA Medicare surcharges two years later — crossing a cliff by $1 can cost thousands per year. (3) Converted funds must season for 5 years before the earnings are penalty-free (the "5-year rule"). This calculator models all three effects.

The strategy pays off primarily when: (a) you're currently in a lower bracket than you expect to be in the future due to RMDs, (b) you want to leave tax-free Roth assets to heirs, or (c) you want to reduce your lifetime Medicare premiums by managing future MAGI.

This calculator shows a recommended conversion amount for each year, the tax cost, and how your account balances evolve over your planning horizon. Adjust the strategy inputs to find the approach that makes sense for your situation.

5 Tips to Maximize Your Conversion Window

1

Start before RMDs begin

The conversion window closes at 73 when RMDs begin. The earlier you start (even at 60–65), the lower your required conversion amount each year and the more time your Roth has to grow tax-free.

2

Watch the IRMAA cliffs

Your conversion in 2026 determines your Medicare premium in 2028. Enable the IRMAA cap to ensure conversions never cross a tier boundary. Single: $109k / $137k / $171k / $205k / $500k. MFJ: $218k / $274k / $342k / $410k / $750k.

3

Account for the Social Security torpedo

If you collect SS, large conversions can push more of your SS into taxation — effectively raising your marginal rate well above the bracket rate. This calculator models the SS torpedo effect when computing your conversion ceiling.

4

Use the bridge fund strategically

Conversion taxes come due in April. Fund them from your taxable brokerage, not from the Roth itself. Selling appreciated taxable assets (at potentially favorable long-term capital gains rates) to fund conversion taxes is often more efficient than pulling from the Roth.

5

Consider QCDs at 70½

Qualified Charitable Distributions let you direct up to $105,000/year from your IRA to charity without it counting as taxable income. QCDs can satisfy your RMD obligation while keeping your MAGI low — creating more room for additional Roth conversions.

Check your IRMAA exposure: Roth conversions increase your MAGI and can push you over an IRMAA Medicare surcharge cliff two years later. Use the Medicare IRMAA Calculator to see exactly how much headroom you have before the next cliff.

Watch for the SS torpedo: Large IRA withdrawals or Roth conversions can trigger 85% SS taxation, pushing your effective marginal rate to 40%+. See the Social Security Tax Torpedo Calculator for a detailed marginal rate breakdown.

Frequently Asked Questions

A Roth conversion ladder converts traditional IRA money into a Roth IRA over several years, paying taxes now at a controlled rate. Retirees do this to reduce future Required Minimum Distributions (which can push them into higher brackets), to pass on tax-free assets to heirs, and to manage Medicare IRMAA surcharges — which are based on income from two years prior.
The ideal window is between early retirement (when earned income drops) and age 73 (when RMDs begin). During this window, your taxable income is often at its lowest, making conversions cheapest. If you're collecting Social Security, be aware that large conversions can push more SS income into taxation — the calculator models this effect.
Each Roth conversion starts its own 5-year clock. Converted amounts (not earnings) can always be withdrawn penalty-free after age 59½. But earnings on converted amounts must wait 5 years from the conversion date before they can be withdrawn tax-free. If you're 59½ or older, the penalty concern is mostly moot — the main 5-year rule that matters is on earnings.
IRMAA is calculated on your MAGI from two years prior. Roth conversions are treated as ordinary income and count toward MAGI. A large conversion in Year 1 shows up as a higher Medicare premium in Year 3. The "cap at IRMAA cliff" feature in this calculator limits your conversion each year to avoid crossing the next IRMAA tier boundary, which can save thousands in Medicare premiums.
If you're receiving Social Security, large IRA withdrawals or Roth conversions can trigger more of your SS benefit to be taxable (up to 85%). This can effectively make your marginal tax rate 40–50% higher than the bracket rate suggests — the "torpedo" effect. This calculator accounts for SS taxation when finding your optimal conversion amount.
Required Minimum Distributions are mandatory annual withdrawals from traditional IRAs starting at age 73, calculated as your account balance divided by an IRS life-expectancy factor. If your traditional IRA grows large, RMDs can force substantial taxable income in your 70s and 80s — potentially at higher rates than conversions done earlier. Converting now at a known rate can be far cheaper than paying higher rates on forced RMDs later.
The bridge fund is your taxable brokerage or savings account used for living expenses during the conversion window. Since Roth conversions increase your taxable income without providing spendable cash, you need another source for living costs while you convert. The bridge fund covers the gap between your income (pension, Social Security, RMDs) and your spending needs, plus the tax bill on conversions. When the bridge fund is depleted, the strategy becomes harder to sustain.
It depends on your future RMD trajectory and expected future rates. If your projected RMDs would push you into the 24%+ bracket, converting to the top of 22% now is a clear win. If your RMDs are modest, filling to the top of 12% may be sufficient. Use the calculator to see how account balances change across scenarios — a larger annual conversion depletes the traditional IRA faster and reduces future RMDs, but costs more tax today.