How the Roth vs. Traditional Calculator Works
This calculator models both account types simultaneously using the same contribution rate, employer match, return assumption, and time horizon. The key distinction is tax treatment: Traditional contributions reduce current taxable income using 2024 federal brackets, while Roth contributions are made post-tax. At retirement, the Traditional balance is multiplied by (1 − estimated retirement tax rate) to find after-tax wealth, while the Roth balance is taken at face value since qualified withdrawals are tax-free.
Head-to-Head Tab
Side-by-side account cards show nominal balance, after-tax value, annual contribution, current tax savings, and per-year take-home cost for each strategy. A stacked area chart shows after-tax wealth diverging over time, with the verdict and break-even rate prominently displayed.
Withdrawal Comparison Tab
Models annual withdrawals from both accounts using your specified withdrawal rate and period. Traditional withdrawals are taxed at your expected retirement rate; Roth withdrawals are tax-free. Cumulative net income and annual withdrawal bar charts show the full picture over a 30-year retirement horizon.
Break-Even Finder Tab
Sweeps retirement tax rates from 0% to 40% and charts the Roth advantage at each rate. The zero-crossing is your break-even rate. Bars above the x-axis mean Roth wins at that rate; bars below mean Traditional wins. Your current and expected rates are highlighted for instant context.
Contribution Mode Toggle
"Same dollar" mode contributes an identical dollar amount to both. Roth costs more take-home pay because it has no upfront tax offset. "Same cost" mode adjusts the Roth contribution downward so both strategies reduce take-home pay by the same amount — isolating the pure tax-timing decision from the quantity decision.
Roth vs. Traditional 401(k): Core Tax Differences
| Feature | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Contribution tax treatment | Pre-tax (reduces taxable income) | After-tax (no current deduction) |
| Current-year tax benefit | Yes — saves taxes now | No |
| Investment growth | Tax-deferred | Tax-free |
| Withdrawals in retirement | Taxed as ordinary income | Qualified withdrawals tax-free |
| Required Minimum Distributions | Required at age 73 | Exempt (as of 2024, SECURE 2.0) |
| Income limit to contribute | None | None (unlike Roth IRA) |
| 2024 contribution limit | $23,000 ($30,500 age 50+) | $23,000 ($30,500 age 50+) |
| Employer match tax treatment | Always pre-tax | Always pre-tax (even on Roth contributions) |
| Best if retirement tax rate... | Lower than current rate | Higher than current rate |
RMDs and SECURE 2.0: A Roth 401(k) Advantage
The SECURE 2.0 Act of 2022 eliminated Required Minimum Distributions from Roth 401(k) accounts starting in 2024. Previously, both Traditional and Roth 401(k) accounts were subject to RMDs at age 73 — a significant disadvantage of the Roth 401(k) compared to the Roth IRA. That disadvantage is now gone. Here is what this means in practice:
Roth 401(k) — No RMDs
As of 2024, Roth 401(k) accounts are fully exempt from Required Minimum Distributions. You can leave funds invested and growing tax-free indefinitely, or pass the account to heirs who inherit the tax-free growth.
Traditional 401(k) — RMDs Required
You must begin withdrawing a minimum amount annually at age 73, calculated based on your account balance and IRS life expectancy tables. RMD income is taxed as ordinary income and may push you into higher brackets or trigger Medicare IRMAA surcharges.
Estate Planning Implications
Roth 401(k) accounts with no RMDs allow the full tax-free balance to pass to heirs. Heirs can use the 10-year rule to spread tax-free withdrawals. Traditional 401(k) heirs face the same 10-year rule but on fully taxable distributions.
Roth vs. Traditional Calculation Examples
Example 1: Early career, lower bracket — Roth wins
A 26-year-old earning $55,000, filing single, is in the 22% bracket today. They contribute 6% over 39 years at 7% return. If their retirement income (from Social Security, RMDs, etc.) keeps them in the 22%+ bracket, Roth generates more after-tax wealth. The break-even rate is around 18% — well below their expected retirement rate, making Roth the stronger choice.
Example 2: Peak earner, high bracket — Traditional wins
A 48-year-old earning $280,000, married filing jointly, is in the 35% bracket today. They expect retirement income to be far lower — perhaps $120,000/yr — putting them in the 22% bracket at retirement. The Traditional 401(k) lets them defer at 35% and pay at 22%, a 13-point advantage that easily outweighs the Roth's tax-free growth benefit over 17 years.
Example 3: Uncertain future — split strategy
A 38-year-old earning $110,000 in the 22% bracket is unsure whether tax rates will rise or fall by retirement. They split contributions: 50% to Traditional (locking in current deductions) and 50% to Roth (building tax-free reserves). This hedges against both scenarios — if rates rise, the Roth pool wins; if rates fall, the Traditional pool wins.
Frequently Asked Questions
What is the main difference between a Roth and Traditional 401(k)?+
The core difference is timing of taxation. Traditional 401(k) contributions are made pre-tax — they reduce your taxable income today, but withdrawals in retirement are taxed as ordinary income. Roth 401(k) contributions are made with after-tax dollars — no current-year deduction — but qualified withdrawals in retirement are completely tax-free, including all investment growth.
Which is better: Roth or Traditional 401(k)?+
It depends on whether your tax rate will be higher now or in retirement. If you expect to pay a higher tax rate in retirement than you do today, Roth is generally better — you pay tax now at a lower rate and withdraw tax-free later. If you expect to be in a lower bracket in retirement, Traditional is usually better — you defer tax now at a higher rate and pay at a lower rate later. Our break-even finder identifies the exact retirement tax rate at which both strategies tie.
What is the break-even tax rate for Roth vs. Traditional?+
The break-even rate is the retirement marginal tax rate at which both strategies produce identical after-tax wealth. If your expected retirement tax rate exceeds the break-even rate, Roth wins. If it is below the break-even rate, Traditional wins. The break-even rate depends on your current salary, contribution rate, years to retirement, and investment return assumptions.
Can I contribute to both a Roth and Traditional 401(k) in the same year?+
Yes. Many plans allow you to split contributions between traditional (pre-tax) and Roth (after-tax) sub-accounts within the same 401(k). The combined total across both cannot exceed the annual IRS limit of $23,000 (2024) or $30,500 for those aged 50 and older. This split strategy can hedge against future tax rate uncertainty.
Do Roth 401(k) accounts have Required Minimum Distributions?+
As of 2024, under the SECURE 2.0 Act, Roth 401(k) accounts are exempt from Required Minimum Distributions (RMDs). Previously, Roth 401(k) accounts were subject to RMDs (unlike Roth IRAs), but this distinction was eliminated. This makes the Roth 401(k) more attractive for those who want to keep funds invested tax-free into their 70s and beyond, or pass the account to heirs.
Is there an income limit for contributing to a Roth 401(k)?+
No. Unlike Roth IRAs, which phase out for high earners (above $146,000 single / $230,000 married in 2024), there is no income limit for Roth 401(k) contributions. Any employee eligible for the 401(k) plan can designate all or part of their contributions as Roth, regardless of income.
How does the employer match work with a Roth 401(k)?+
Employer matching contributions to a 401(k) are always made on a pre-tax basis, even when matched against your Roth contributions. This means your employer match goes into the traditional (pre-tax) side of your 401(k) and will be taxed when withdrawn in retirement, regardless of whether you are making Roth contributions. Both calculators model this correctly.
What happens to Roth 401(k) funds if I change jobs?+
You can roll Roth 401(k) funds directly into a Roth IRA, which preserves their tax-free status and eliminates future RMD requirements. Alternatively, you can roll them into a new employer's Roth 401(k) if the new plan accepts Roth rollovers. Rolling to a traditional IRA or converting to a traditional account would be a taxable event.
What are qualified withdrawals from a Roth 401(k)?+
A Roth 401(k) distribution is qualified (and therefore tax-free and penalty-free) if: (1) the account has been held for at least 5 years, and (2) the distribution occurs after you reach age 59½, become disabled, or die. Non-qualified distributions may be subject to income tax and a 10% early withdrawal penalty on the earnings portion.
Does contributing the same dollar amount to Roth cost more out of pocket?+
Yes. Because traditional 401(k) contributions reduce your taxable income and generate immediate federal tax savings, they cost less in take-home pay per dollar contributed. Contributing the same dollar amount to a Roth 401(k) has no upfront tax offset, so your paycheck is reduced by the full contribution. Our calculator offers a 'same take-home cost' mode to model equal out-of-pocket scenarios.
Estimates & Assumptions
- Federal income tax estimated using 2024 marginal brackets and the standard deduction for your filing status. State income taxes are not modelled; some states do not tax retirement income, which would further alter the comparison.
- Traditional after-tax wealth at retirement is estimated by applying the single retirement tax rate you specify uniformly to the full balance. Actual tax liability depends on withdrawal strategy, other income sources, and applicable brackets in each withdrawal year.
- Employer matching contributions are modelled as pre-tax for both account types, consistent with current US IRS rules. Employer match distributions are therefore taxable for both Traditional and Roth participants.
- Roth 401(k) qualified withdrawal rules require both a 5-year holding period and age 59½ or older. This calculator assumes all modelled withdrawals meet qualified distribution criteria.
- The break-even rate is computed by incrementing the retirement tax rate in 0.5% steps. Results are projections based on fixed assumptions and do not account for future tax law changes, variable investment returns, or changes in salary and contribution behaviour over time.
This calculator is for educational and estimation purposes only. The Roth vs. Traditional decision is one of the most impactful in retirement planning and depends on factors specific to your financial situation, state of residence, and retirement income plan. Consult a certified financial planner or tax advisor before making contribution allocation decisions.