Roth Conversion Calculator

Model year-by-year Traditional → Roth conversions with real tax brackets, RMDs, and Social Security taxation. All amounts in today's dollars.

About you

These drive the tax tables, RMD start age, and Social Security rules used throughout the model.

Birth year Age: —

Filing status

Plan through age

Based on birth year: RMD starts at age —, Social Security Full Retirement Age is —.

All dollar amounts in today's dollars; the model inflates them forward.

Traditional IRA / 401(k) All pre-tax retirement money

Existing Roth balance

Taxable / brokerage account Pays conversion taxes

Other annual taxable income Interest, dividends, rental

Annual wages (gross)

Annual 401(k) / pre-tax contribution Reduces wages, adds to Trad

Retirement age Wages stop after this age

Annual retirement spending

Your monthly benefit at FRA Check ssa.gov for your estimate

Claim age Percent shown assumes FRA of 67; slight shift if your FRA differs

Spouse's monthly SS at FRA (MFJ only) Assumes same claim age

Nominal investment return (% / yr)

Inflation (% / yr) Also inflates tax brackets

Pick a strategy. The model fills the bracket each year up to its top while accounting for SS taxation and other income.

Strategy

Start converting at age Usually retirement age or 59½, whichever is later

Stop converting at age Last year before RMDs typically start

Custom annual amount (today's $)

What this model does — and doesn't

Federal tax only. State income tax is not modeled — if you're in a state with income tax, add your marginal rate to each conversion's cost.
Brackets: 2025 IRS statutory tables, inflated forward at your assumption rate.
RMD start age is derived from your birth year (73 if born 1951–1959, 75 if born 1960 or later per SECURE 2.0).
SS taxation thresholds ($25k / $34k single & HoH; $32k / $44k MFJ) do not adjust for inflation — this is by law and means more of your SS becomes taxable over time (accurately modeled).
IRMAA (Medicare surcharges) not modeled. Conversions past age 63 can push you into higher Medicare Part B/D premiums two years later. Watch the income cliffs (roughly $103k / $129k / $161k / $193k single).
"Fill to bracket" iterates to handle the feedback loop where conversion → more SS taxable → less conversion room.
Tax paid from taxable account. Standard best practice — paying conversion tax from within the IRA usually eliminates the benefit.
Withdrawal order in retirement: taxable → traditional → Roth.
ACA subsidies not modeled. If you retire before Medicare (65) and use marketplace coverage, big conversions can wipe out subsidies — model separately.
Not tax or financial advice. Run any real conversion plan past a CPA or fee-only advisor before pulling the trigger.