Roth 401(k) Calculator
Keep the current Roth balance separate from any existing Traditional balance. Employee deferrals flow to Roth, while employer contributions flow to the selected Roth or Traditional bucket; both balances then grow monthly and remain separate in the results.
How to use this calculator
Enter current Roth and Traditional balances, employer tax bucket, salary, contribution and match inputs, age, limit growth, return, years, and current and retirement tax rates.
Review combined elective-deferral limits, employer contribution treatment, qualified-distribution rules, match, vesting, fees, and uncertain future tax law.
Read projected Roth and Traditional balances, regular and catch-up contributions, combined after-tax value, and estimated current Roth tax cost.
Formula
Qualified Roth value is modeled without withdrawal tax; Traditional after-tax value = Traditional balance × (1 − retirement tax rate). Combined after-tax value adds those buckets, while current Roth tax cost uses the entered marginal rate.
Worked example
If $5,000 of Roth assets and $5,000 of Traditional assets each grow to $10,000, a 20% retirement-tax assumption values them at $10,000 and $8,000, or $18,000 combined.
Assumptions and limits
- Qualified Roth treatment and tax rates are assumptions; employer contributions use the selected bucket, and actual plan eligibility, Roth employer options, vesting, taxes, and fees may differ.
- Roth 401(k) Calculator treats the entered values as estimates and does not infer missing project, account, or personal details.
- Calculations retain working precision except where the cited method requires an intermediate rounding step; displayed values are then formatted separately. Source rules and dated rates must be rechecked when they change.
Sources
- Internal Revenue Service: Designated Roth AccountsDesignated Roth contribution and distribution rules. Reviewed 2026-08-14.
- U.S. Securities and Exchange Commission: Compound Interest CalculatorCompound-growth inputs and future-value concepts. Reviewed 2026-08-14.
- Internal Revenue Service: 401(k) and profit-sharing plan contribution limitsOfficial formula or method source used by this calculator. Reviewed 2026-08-14.
- Internal Revenue Service: Retirement topics: Catch-up contributionsOfficial formula or method source used by this calculator. Reviewed 2026-08-14.
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Verification
How this calculator is checked
Trust comes from reproducible evidence, not model confidence. You can inspect the formula, assumptions, worked example, and cited sources on this page.
- Versioned calculationFormula logic is kept separate from the interface and covered by automated registry and behavior checks.
- Cited evidenceSources linked for independent checking: 4.
- Transparent AI useAI may assist drafting or adversarial review. Agreement between models is not proof, and no human expert review is claimed unless a named reviewer is shown.
Frequently asked questions
How does the Roth 401(k) Calculator work?
Qualified Roth value is modeled without withdrawal tax; Traditional after-tax value = Traditional balance × (1 − retirement tax rate). Combined after-tax value adds those buckets, while current Roth tax cost uses the entered marginal rate.
What information should I enter in the Roth 401(k) Calculator?
Enter current Roth and Traditional balances, employer tax bucket, salary, contribution and match inputs, age, limit growth, return, years, and current and retirement tax rates, then verify combined elective-deferral limits, employer contribution treatment, qualified-distribution rules, match, vesting, fees, and uncertain future tax law.
What should I verify before using this Roth 401(k) Calculator result?
Qualified Roth treatment and tax rates are assumptions; employer contributions use the selected bucket, and actual plan eligibility, Roth employer options, vesting, taxes, and fees may differ.
Last updated 2026-08-25 · 2026-monthly-retirement-projection-v4 · content-2026-08-14 · Published by YunFanLabs