Workplace retirement contribution scenario
Roth vs. traditional 401(k) scenario calculator
Compare Roth and traditional 401(k) contributions using the same take-home pay budget, tax-rate assumptions, return, and time horizon.
Compare two 401(k) contribution scenarios that use the same monthly reduction in take-home pay. The traditional contribution is grossed up using your entered current tax rate; the Roth contribution equals the take-home amount. Both use the same return and time assumptions.
Enter assumptions to compare modeled contributions and after-tax balances.
How the comparison works
The selected monthly amount represents the take-home pay reduction in both scenarios. The traditional 401(k) contribution is calculated as that amount ÷ (1 − current tax-rate assumption); the Roth contribution equals the selected amount. Each contribution is deposited at month-end and earns the same fixed annual return ÷ 12 for the entered number of months. The traditional balance is then reduced by the retirement distribution tax-rate assumption. The Roth result assumes a qualified distribution, whose earnings are generally tax-free under IRS rules.
This is a simplified federal income-tax scenario, not an estimate of your tax bill. Your marginal tax rate may not equal the tax effect of a contribution; state and local taxes, deductions, credits, tax-bracket changes, contribution limits, fees, investment choices, employer matching, vesting, inflation, and distribution rules can change the comparison. It does not predict your future tax bracket or determine whether a distribution will qualify. Check whether your plan offers both contribution types and review current plan and tax information. Sources checked November 3, 2026: IRS guidance on designated Roth accounts in retirement plans and tax treatment of retirement plan contributions.
This calculator compares entered assumptions only. It is not tax, investment, or retirement advice.
Related retirement planning
Estimate a plan's entered employer-match tiers with the 401(k) employer-match planner. For SSA benefit estimates, see the Social Security retirement estimate guide.
How it works
Enter a monthly take-home amount to allocate, current and retirement tax-rate assumptions, an investment horizon, and a fixed annual return assumption. The model compares a traditional pre-tax contribution grossed up to the same take-home cost with a Roth contribution equal to that amount.
Good to know
How does this compare the two contribution types fairly?
It holds the modeled monthly reduction in take-home pay equal. The traditional contribution is grossed up by dividing that amount by one minus the entered current tax rate; the Roth contribution equals the take-home amount.
Does this predict my future tax rate or tax savings?
No. You enter both tax-rate assumptions. The model does not prepare a tax calculation, predict a future bracket, or account for all deductions, credits, state taxes, or individual circumstances.
Are Roth 401(k) withdrawals always tax-free?
No. The Roth result assumes a qualified distribution. IRS rules include a five-taxable-year period and other qualifying conditions; check current IRS guidance and your plan terms.
Does the tool include an employer match or contribution limits?
No. It compares employee contributions only and excludes employer match, vesting, plan limits, fees, inflation, and changing returns.
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