Roth Converter

Pick a few annual conversion amounts. See the tax cost and 401(k) balance over the next 10 years across multiple rate-of-return scenarios.

YouAgeYour age today. Drives the per-year age series and RMD eligibility.Filing statusFederal filing status. Sets bracket widths and the standard deduction.Annual other taxable incomeAnything taxed at ordinary-income rates that you receive each year, separate from the 401(k) being converted. Held flat across the horizon (v1).Include:

W-2 wages, self-employment / consulting income
Pension, annuity, Traditional IRA withdrawals
Taxable interest (savings, CDs, bonds), ordinary dividends
Rental income, K-1 pass-through, royalties

Do NOT include:

Roth / HSA qualified withdrawals (tax-free)
Long-term capital gains, qualified dividends (different rates)
Social Security (v1 does not model the taxable-portion rules)
The Roth conversion itself (calculator adds it on top)

Tax year (for brackets)Year of the tax tables to use (default 2026). v1 applies the same brackets every projected year.

401(k)Traditional 401(k) balancePre-tax 401(k) today. Conversions are pulled from this bucket and taxed as ordinary income the year they happen.Roth 401(k) balanceAlready-taxed Roth 401(k) today. Grows tax-free; converted dollars land here.

Total 401(k)

$1.00M

Traditional 70% / Roth 30%

Include RMDs at age 73/75 (SECURE Act 2.0)Forces Required Minimum Distributions once you hit RMD age (73 if born 1951-1959, 75 if born 1960+). RMDs leave the system and reduce ending balance.

ScenariosHorizon (years)Years to project starting this year (default 10).Rates of return (%)Comma-separated annual rates to sweep. Same nominal rate applied to Traditional and Roth. Each rate runs as a separate scenario so you can see how sensitive the outcome is to the assumption you can't pin down.Realistic bounds:

5% - conservative / bond-heavy / pessimistic decade
7% - long-term real S&P 500 average
9% - close to long-term nominal S&P average
11% - optimistic upside

Rule of 72: years to double a balance is roughly 72 / rate. At 5% it doubles in ~14 years; at 7%, ~10 years; at 10%, ~7 years.Annual conversion cases ($)Each number is a separate strategy, not a per-year amount. The strategy converts that same dollar amount every year of the horizon. So 50000 means "convert $50k each year for 10 years", totaling up to $500k converted (capped by your Traditional balance once it runs out).Other rules:

$0 baseline is always added so every other row reads as a delta from doing nothing.
Each year's conversion is capped by Traditional balance after RMD; once Traditional is empty, conversion drops to $0 for remaining years.
Tax is paid from outside the 401(k), so 100% of the conversion lands in Roth.

v1 does not optimize the path year-by-year (e.g., "$100k in years 1-3, then $50k") - that is a v2 feature.