Roth 401(k) Calculator: Compare Roth and Traditional Contributions
Use this guide to understand the assumptions, inputs, results, and next steps behind the calculator.
Created by Luis Gonzalez · Last updated August 25, 2026
A Roth 401(k) contribution is made from after-tax pay, while a traditional 401(k) contribution is generally made before federal income tax. The Roth-versus-traditional choice is largely a tax-timing decision: pay tax now or defer it until eligible withdrawals. This calculator estimates retirement balances under both approaches and compares them using your current and expected retirement tax brackets.
With the default inputs—$100,000 salary, a 10% contribution rate, age 35, and retirement at 65—the calculator uses a $10,000 annual employee contribution and a $4,000 annual employer match. Its reported Roth balance at retirement is $1,322,451, traditional after-tax balance is $1,192,650, estimated tax savings in retirement are $27,783, and break-even year is age 49. These are model outputs based on fixed return and tax assumptions, not guaranteed balances.
Set the tax and savings assumptions
Enter salary and contribution rate first. Then add current age, planned retirement age, expected annual investment return, current and retirement tax brackets, employer match, and state tax rate. Select catch-up eligibility only if it applies to your age and plan.
The calculator uses your contribution rate to estimate employee deferrals and assumes the employer match is a separate contribution. For a paycheck-level view of savings, use the Roth 401(k) contribution calculator or the 401(k) contribution calculator. To project a general workplace plan, compare the 401(k) calculator and the 401(k) compound interest calculator.
Default example: why the Roth estimate is higher
The model assumes a 30-year period from age 35 to 65, a 7% annual return, a 24% current federal bracket, a 22% retirement bracket, and a 5% state tax rate. It therefore uses combined rates of 29% now and 27% in retirement.
The employee contribution calculation is $100,000 × 10% = $10,000 per year. Employer match is $100,000 × 4% = $4,000 per year. The calculator's projection reports $1,322,451 for the Roth balance at retirement and $1,192,650 for the traditional after-tax balance. Subtracting the reported results gives $1,322,451 − $1,192,650 = $129,801, but the calculator's “Tax Savings in Retirement” result is $27,783. These outputs reflect different internal comparisons: the displayed Roth balance includes the Roth contribution and employer balance, while the after-tax comparison adjusts employer and traditional amounts. Use the named result cards for their intended comparison rather than treating the raw balance difference as the tax-savings card.
The model identifies age 49 as the first year the Roth after-tax value exceeds the traditional after-tax value in its annual projection. That break-even age is sensitive to tax assumptions, contribution amounts, returns, and how the model treats the employer match.
| Scenario inputs | Contribution and match | Expected effect in this model |
|---|---|---|
| Salary $80,000; contribution 6%; match 3% | $4,800 employee contribution; $2,400 match | Lower contributions generally reduce both projected balances |
| Salary $120,000; contribution 10%; match 4% | $12,000 employee contribution; $4,800 match | Higher contributions generally increase both balances |
| Current bracket 22%; retirement bracket 24% | Tax rate expected to rise | Roth tax treatment becomes relatively more attractive |
| Current bracket 32%; retirement bracket 22% | Tax rate expected to fall | Traditional tax deferral may become relatively more attractive |
The comparison rows illustrate directional effects, not calculator-generated balances. A scenario needs all inputs and the calculator's full computation to produce a precise output.
Tax treatment and 2026 contribution limits
Roth employee contributions are included in taxable income now; qualified Roth distributions can be tax-free if distribution rules are met. Traditional employee deferrals generally reduce current federal taxable income, while withdrawals are usually taxable. The IRS explains workplace-plan Roth accounts in its designated Roth account guidance.
For 2026, the employee elective deferral limit for most 401(k) plans is $24,500. The general age-50 catch-up is $8,000, and eligible participants ages 60–63 may have a higher $11,250 super catch-up under SECURE 2.0, subject to plan rules. The total employee-and-employer defined contribution limit is generally $72,000, before applicable catch-up contributions. See the IRS 2026 retirement plan limits for current limits. The calculator caps employee contributions using its 2026 limit assumptions; the employer match is modeled separately.
Employer matching contributions are generally deposited as pre-tax money even when your own deferrals are Roth. That means part of the account may still be taxable on withdrawal. The calculator reflects this distinction by taxing the employer balance at the assumed retirement tax rate. Review your plan’s rules and vesting schedule; the Roth 401(k) withdrawal calculator can help estimate withdrawals after retirement.
How the comparison is calculated
Years to retirement = max(0, retirement age - current age)
Annual employee contribution = min(salary × contribution rate, applicable 2026 limit)
Annual employer match = salary × employer match rate
Traditional after-tax value =
traditional account balance × (1 - retirement tax rate)
+ after-tax value of tax savings invested outside the plan
The default total tax assumptions are 24% + 5% = 29% current and 22% + 5% = 27% at retirement. The employee deferral is $100,000 × 10% = $10,000, and the match is $100,000 × 4% = $4,000. The model then compounds each account annually at 7% for 30 years and applies the assumed retirement tax to the taxable balances. It treats tax savings on traditional contributions as invested in a side account, with a modeled 15% reduction to the annual return on that side account.
Choosing between Roth and traditional
A Roth contribution can suit someone who expects a higher tax rate later, values tax-free qualified withdrawals, or wants to diversify future taxable income. A traditional contribution can suit someone who benefits from a larger deduction today and expects a lower marginal rate in retirement. Neither choice is universally better: future tax law, state of residence, pension income, Social Security, and required distributions may change the comparison.
Try changing one assumption at a time. For instance, move retirement tax bracket from 22% to 30% while holding other inputs constant, then reverse the experiment. Also test lower and higher returns; the same tax-rate difference can produce a different result when contributions compound for decades. A 401(k) max contribution calculator helps check deferral capacity, while the 401(k) future value calculator focuses on account growth.
Roth 401(k) accounts are subject to distribution rules, and plan features differ. If you may roll funds after leaving a job, compare a 401(k)-to-Roth IRA conversion and read about how 401(k) withdrawals are taxed. Similar Roth-versus-traditional choices apply to some public-sector plans; compare the Roth 403(b) calculator and Roth 457 calculator.
Frequently asked questions
Does a Roth 401(k) match go into the Roth account?
Not necessarily. Employer matching contributions have generally been treated as pre-tax contributions, so their eventual distributions may be taxable even when your own deferrals are Roth. Confirm the specific plan’s treatment and current rules.
Is a Roth 401(k) always better if I am young?
No. A long horizon gives tax-free growth more time, but the decision also depends on your current tax rate versus the rate on future withdrawals. A young worker in a high bracket who expects a lower retirement bracket may still prefer traditional deferrals.
Should I contribute Roth or traditional if my employer matches?
First contribute enough to receive the full match if that fits your financial circumstances; otherwise, you may leave part of the benefit unused. Then compare Roth and traditional treatment for your own employee contributions. The calculator assumes the match is made in addition to your deferral.
What does the break-even year mean?
It is the first projected age at which the model's Roth after-tax value exceeds the traditional after-tax value. It does not mean you recover a literal Roth “cost” at that age, and it may change substantially with taxes, returns, and contribution behavior.
Are qualified Roth 401(k) withdrawals tax-free?
They can be tax-free when the distribution satisfies applicable qualification rules, including the five-year rule and an age or other qualifying condition. Nonqualified distributions can have different tax treatment.
Does the model account for state taxes?
Yes, it adds the entered state tax rate to the current and retirement federal tax brackets. It does not model specific state deductions, exclusions, credits, or state-by-state treatment.
Next steps
Use your actual plan match, contribution limit, and likely tax brackets rather than relying only on the defaults. Compare the resulting balance with expected income needs using a 401(k) withdrawal calculator and a Roth IRA tax calculator. For the broader tax decision, review Roth versus traditional tax treatment.