Choosing between a Roth 401(k) and a traditional 401(k) can have a significant effect on how much of your retirement savings you ultimately get to keep. Both accounts are designed to help you save for retirement, and both can provide valuable employer matching contributions. However, the two options treat taxes differently.
Roth 401(k) vs 401(k) Calculator
A traditional 401(k) generally allows eligible employee contributions to be made before federal income taxes, potentially reducing taxable income today. Taxes are generally paid when money is withdrawn in retirement. A Roth 401(k), by contrast, uses after-tax employee contributions. You pay applicable income taxes on the money now, while qualified Roth withdrawals can generally be tax-free.
The important question is not simply whether one account is "better." The better choice can depend on your current tax rate, expected retirement tax rate, salary, contribution percentage, employer match, investment return, salary growth, and years until retirement.
Our Roth 401(k) vs 401(k) Calculator helps compare the estimated future and after-tax values of the two options. Enter your personal assumptions, and the calculator estimates the balance you could accumulate under each approach and identifies which option produces the higher modeled after-tax value.
Important: This calculator provides an estimate for educational and planning purposes. Actual investment returns, tax rules, contribution limits, employer matching formulas, fees, withdrawals, and individual circumstances can change your results.
What Is a Roth 401(k)?
A Roth 401(k) is an employer-sponsored retirement account that combines features of a traditional 401(k) with Roth tax treatment.
With Roth contributions, you generally pay income taxes on the money before it enters the account. Once contributed, the money can potentially grow through investments without annual taxation on investment gains inside the account. If the distribution meets the applicable requirements for a qualified Roth distribution, withdrawals can generally be made tax-free.
For someone who expects to be in a similar or higher tax bracket during retirement, paying taxes now may be attractive.
For example, imagine you earn $80,000 per year and decide to contribute 8% of your salary. Your employee contribution would be:
$80,000 × 8% = $6,400
With a Roth 401(k), the contribution is made with after-tax dollars. With a traditional 401(k), the employee contribution generally receives pre-tax treatment for federal income tax purposes.
The difference can become substantial over several decades because the money remaining invested has time to compound.
What Is a Traditional 401(k)?
A traditional 401(k) is a retirement savings account that generally allows eligible employee contributions to be made on a pre-tax basis.
This means contributions can potentially reduce your taxable income today. However, withdrawals are generally subject to ordinary income tax when distributed.
Suppose you contribute $6,400 to a traditional 401(k). The entire contribution can generally enter the account before current federal income tax is considered, subject to applicable rules. You receive the potential tax benefit today, but you may owe taxes when the money is withdrawn later.
This creates a fundamental tax-timing decision:
- Traditional 401(k): Potential tax benefit now, taxes generally paid later.
- Roth 401(k): Taxes generally paid now, qualified withdrawals generally tax-free later.
The Roth 401(k) vs 401(k) decision therefore depends heavily on your expectations about your current and future tax situation.
How the Roth 401(k) vs 401(k) Calculator Works
The calculator uses several inputs to estimate the two retirement scenarios:
- Current age
- Retirement age
- Annual salary
- Employee contribution percentage
- Employer match percentage
- Expected annual investment return
- Current tax rate
- Retirement tax rate
- Annual salary growth
It then estimates the retirement balance for both account types.
The calculator reports:
- Years until retirement
- Traditional 401(k) future balance
- Traditional 401(k) after-tax value
- Roth 401(k) future balance
- Roth 401(k) after-tax value
- Roth advantage or disadvantage
- Estimated better option
This makes it easier to compare the tax consequences instead of looking only at the headline account balance.
How to Use the Roth 401(k) vs 401(k) Calculator
Using the calculator is straightforward.
Step 1: Enter Your Current Age
Enter your current age.
For example:
Current age = 35
The calculator uses this information together with your retirement age to determine how many years your money could remain invested.
Step 2: Enter Your Retirement Age
Enter the age at which you expect to retire.
For example:
Retirement age = 65
If you are 35 today and plan to retire at 65, you have approximately:
65 − 35 = 30 years
for contributions and investment growth.
Step 3: Enter Your Annual Salary
Enter your current annual salary in dollars.
For example:
Annual salary = $80,000
Salary is important because the calculator uses it to determine your employee contributions and employer matching contributions.
Step 4: Enter Your Employee Contribution
Enter the percentage of your salary you plan to contribute.
For example:
Employee contribution = 8%
At an $80,000 salary:
$80,000 × 8% = $6,400
Your contribution is then adjusted for the tax treatment modeled by the calculator.
Step 5: Enter the Employer Match
Enter the employer matching percentage used for your estimate.
For example:
Employer match = 4%
At an $80,000 salary:
$80,000 × 4% = $3,200
Employer matching can be an important part of retirement savings. However, actual employer plans can have more complicated matching formulas, including limits and contribution requirements.
Step 6: Enter the Expected Annual Return
Enter your estimated annual investment return.
For example:
Expected annual return = 7%
Investment returns are uncertain. A projected return should be viewed as an assumption rather than a guarantee.
Step 7: Enter Your Current Tax Rate
Enter your estimated current tax rate.
For example:
Current tax rate = 22%
This input is particularly important for the Roth scenario because the calculator reduces the employee contribution by the current tax rate to model the after-tax contribution.
Step 8: Enter Your Retirement Tax Rate
Enter your expected tax rate during retirement.
For example:
Retirement tax rate = 20%
The calculator applies this rate to the traditional 401(k) balance when estimating its after-tax value.
The Roth balance is treated as tax-free in the calculator's model, assuming qualified withdrawals.
Step 9: Enter Annual Salary Growth
Enter the percentage by which you expect your salary to grow each year.
For example:
Annual salary growth = 3%
As salary increases, your modeled employee and employer contributions also increase.
Step 10: Click Calculate
After entering all required values, select Calculate.
The calculator will display the estimated results for both retirement account strategies.
Roth 401(k) vs 401(k) Formula
The calculator uses annual contributions and compound growth to model retirement balances.
The basic contribution calculations are:
Employee Contribution
Employee Contribution = Salary × Employee Contribution Rate
For example:
$80,000 × 8% = $6,400
Employer Contribution
Employer Contribution = Salary × Employer Match Rate
For example:
$80,000 × 4% = $3,200
Traditional 401(k) Contribution
The calculator models the traditional contribution as:
Traditional Contribution = Employee Contribution + Employer Contribution
Using the example:
$6,400 + $3,200 = $9,600
The traditional account therefore receives the full modeled employee contribution plus the employer contribution.
Roth 401(k) Contribution
For the Roth calculation, the employee contribution is reduced by the current tax rate in the model:
Roth Employee Contribution = Employee Contribution × (1 − Current Tax Rate)
Then the employer contribution is added:
Roth Contribution = Roth Employee Contribution + Employer Contribution
Using an 8% employee contribution and a 22% current tax rate:
$6,400 × (1 − 0.22) = $4,992
Adding the $3,200 employer contribution:
$4,992 + $3,200 = $8,192
This illustrates why comparing only the account balances can be misleading. The calculator attempts to account for the tax difference affecting the employee's Roth contribution.
Compound Growth Formula
The calculator updates the account balances annually.
The basic calculation is:
New Balance = Previous Balance × (1 + Investment Return) + Annual Contribution
For each year, the calculator:
- Calculates the employee contribution.
- Calculates the employer contribution.
- Adds the appropriate contributions to the account.
- Applies the expected investment return to the existing balance.
- Increases salary according to the annual salary-growth assumption.
- Repeats the process until retirement.
This creates a year-by-year projection rather than simply multiplying the initial contribution by the number of years.
Traditional 401(k) After-Tax Value
The calculator estimates the traditional account's after-tax retirement value using:
Traditional After-Tax Value = Traditional Future Balance × (1 − Retirement Tax Rate)
For example, if the projected traditional balance is $1,000,000 and the assumed retirement tax rate is 20%:
$1,000,000 × (1 − 0.20) = $800,000
The estimated after-tax value would therefore be $800,000.
Roth 401(k) After-Tax Value
The calculator treats the Roth balance as its after-tax value:
Roth After-Tax Value = Roth Future Balance
This assumes the Roth withdrawals meet the requirements for qualified tax-free treatment.
This distinction is central to the comparison. A traditional 401(k) may show a larger nominal balance while having a lower estimated after-tax value once retirement taxes are considered.
Roth Advantage or Disadvantage Formula
The calculator compares the two estimated after-tax values:
Roth Advantage = Roth After-Tax Value − Traditional After-Tax Value
If the result is positive, the model indicates an advantage for the Roth 401(k).
If the result is negative, the traditional 401(k) produces the higher modeled after-tax value.
If the difference is approximately zero, the calculator reports the options as approximately equal.
Roth 401(k) vs 401(k) Example
Consider a 35-year-old worker with these assumptions:
| Input | Example Value |
|---|---|
| Current Age | 35 |
| Retirement Age | 65 |
| Annual Salary | $80,000 |
| Employee Contribution | 8% |
| Employer Match | 4% |
| Expected Annual Return | 7% |
| Current Tax Rate | 22% |
| Retirement Tax Rate | 20% |
| Annual Salary Growth | 3% |
| Years Until Retirement | 30 |
The employee contribution in the first year is:
$80,000 × 8% = $6,400
The employer contribution is:
$80,000 × 4% = $3,200
The traditional contribution modeled in the first year is therefore:
$6,400 + $3,200 = $9,600
For the Roth scenario, the employee's modeled after-tax contribution is:
$6,400 × 78% = $4,992
Adding the employer contribution gives:
$4,992 + $3,200 = $8,192
The calculator then repeats this process over 30 years while increasing salary by 3% annually and applying the assumed 7% annual investment return.
The final comparison depends on the interaction between contribution amounts, investment growth, and tax rates.
Why Your Tax Rate Matters So Much
Tax rates are one of the most important variables in a Roth-versus-traditional decision.
Consider two simplified situations.
Scenario A: Higher Tax Rate Today
Suppose you are currently paying a relatively high tax rate but expect your retirement taxable income to be considerably lower.
In this situation, the traditional 401(k) may be attractive because you potentially receive the tax deduction when your tax rate is higher and pay taxes later when your rate may be lower.
Scenario B: Lower Tax Rate Today
Suppose you are early in your career and currently have a relatively low taxable income, but you expect your earnings and retirement income to increase significantly.
A Roth 401(k) can be attractive because you pay taxes on contributions while your tax rate may be relatively low and potentially receive tax-free qualified withdrawals later.
These are simplified examples. Your actual tax situation may involve multiple federal and state tax brackets, deductions, credits, Social Security taxation, required distributions, and other sources of income.
Factors That Can Affect the Roth vs Traditional Decision
The calculator is useful for comparing assumptions, but several real-world considerations should also be evaluated.
1. Your Current Tax Bracket
Your current marginal tax rate affects the potential value of traditional contributions and the tax cost associated with Roth contributions.
The higher your current tax rate, the more valuable the immediate tax deduction of traditional contributions can potentially become.
2. Your Expected Retirement Tax Rate
The traditional account's future tax cost depends on how much taxable income you have during retirement.
Retirement income could come from:
- 401(k) withdrawals
- IRA distributions
- Pension income
- Social Security
- Investment income
- Rental income
- Part-time employment
- Other taxable sources
Your retirement tax rate may therefore be very different from your current rate.
3. Employer Matching
Employer contributions can substantially increase retirement savings.
A particularly important point is that employer matching contributions may have different tax treatment from your Roth employee contributions. The calculator assumes employer matching contributions are pre-tax in both scenarios.
Your actual plan documents should be checked to understand exactly how your employer's matching contribution works.
4. Years Until Retirement
Time is one of the strongest factors affecting compound growth.
Someone with 35 years until retirement has considerably more time for contributions and investment earnings to compound than someone with only 10 years remaining.
Even relatively small annual differences can become significant over long periods.
5. Salary Growth
If your salary rises over time, percentage-based contributions can increase as well.
For example, with a 3% annual salary-growth assumption, a $80,000 salary becomes approximately:
$80,000 × (1.03)^10 ≈ $107,510
after 10 years.
Higher salaries can therefore lead to larger future contributions when contribution percentages remain constant.
Roth 401(k) vs Traditional 401(k): Quick Comparison
| Feature | Roth 401(k) | Traditional 401(k) |
|---|---|---|
| Employee contribution tax treatment | After-tax | Generally pre-tax |
| Tax benefit today | Generally no deduction for Roth contribution | Potential tax deduction |
| Investment growth | Tax-deferred within account | Tax-deferred within account |
| Qualified withdrawals | Generally tax-free | Generally taxable |
| Employer matching | Depends on plan; generally separate tax treatment | Generally pre-tax |
| Main tax advantage | Potential tax-free qualified retirement withdrawals | Potential tax savings today |
| Best suited to | People expecting higher future tax rates may find it attractive | People expecting lower future tax rates may find it attractive |
| Main uncertainty | Paying taxes today | Paying taxes later |
The exact rules depend on your retirement plan, tax situation, and applicable law.
Benefits of Using a Roth 401(k) vs 401(k) Calculator
A calculator can make an otherwise complicated comparison easier to understand.
It Converts Percentages Into Dollars
Instead of thinking only about "8% contribution" or "22% tax rate," you can see how those assumptions affect projected retirement values.
It Highlights the Tax Difference
The calculator doesn't stop at the future account balance. It also estimates after-tax values.
It Accounts for Salary Growth
Increasing salary can increase future contributions, making the projection more realistic than a simple fixed-contribution calculation.
It Shows the Effect of Time
Changing your retirement age can demonstrate how additional years of contributions and compound growth affect the projected outcome.
It Supports Scenario Testing
You can run multiple scenarios by changing one assumption at a time.
For example:
- 5% return vs. 7% return
- 20% vs. 25% retirement tax rate
- 2% vs. 4% salary growth
- Retirement at 60 vs. 65
- 6% vs. 10% contribution rate
This can help you understand which assumptions matter most.
How to Get More Useful Results
The quality of a retirement projection depends heavily on the assumptions you enter.
Use a Realistic Investment Return
Avoid assuming extremely high returns simply because they produce a more attractive result. Investment performance varies, and actual returns can be negative in some years.
Testing several return assumptions is usually more informative.
Review Your Employer's Matching Formula
Don't assume that an advertised "4% match" automatically means your employer contributes 4% of your entire salary under every circumstance. Matching formulas can include eligibility requirements and contribution thresholds.
Compare Multiple Tax Scenarios
Rather than entering only one retirement tax rate, consider running several scenarios.
For example:
- 15%
- 20%
- 25%
- 30%
This can reveal whether your result is highly sensitive to future taxation.
Consider State Taxes
The calculator focuses on the assumptions entered and does not automatically determine every federal and state tax consideration. If you live in a state with income tax, state taxation can affect the real-world comparison.
Review Your Results Periodically
Retirement planning is not a one-time calculation. Your salary, contribution rate, investment allocation, tax situation, retirement date, and financial goals can all change.
Recalculate periodically as your circumstances change.
Important Limitations of This Calculator
The calculator provides a useful projection, but it should not be treated as a guaranteed prediction.
It does not fully model every possible factor, including:
- Actual investment volatility
- Investment fees
- Specific employer matching formulas
- Annual contribution limits
- Catch-up contribution rules
- State income taxes
- Changes in federal tax law
- Tax credits and deductions
- Social Security benefits
- Pension income
- Required distributions
- Early-withdrawal penalties
- Account withdrawals before retirement
- Changing contribution percentages
- Different investment allocations
- Market downturns
- Sequence-of-returns risk
The model also assumes a consistent annual investment return and salary-growth rate. Real markets and careers rarely follow a perfectly consistent pattern.
For that reason, the calculator is most useful as a planning and comparison tool, not a prediction of your actual retirement balance.
Roth 401(k) vs 401(k): Which One Is Better?
There is no universal winner.
A traditional 401(k) may be attractive when you value tax savings today and expect your effective tax rate in retirement to be lower.
A Roth 401(k) may be attractive when you are willing to pay taxes today in exchange for potentially tax-free qualified withdrawals later.
Some investors may also benefit from using both types of contributions when their employer plan permits it. This can provide tax diversification by creating retirement assets with different tax characteristics.
The most important question is not simply:
"Which account has the larger balance?"
Instead, consider:
"Which option is expected to leave me with more after-tax retirement spending power?"
That is why the calculator compares after-tax values in addition to projected account balances.
Frequently Asked Questions
1. What is the difference between a Roth 401(k) and a traditional 401(k)?
The primary difference is when taxes are paid. Roth 401(k) contributions are generally made with after-tax money, while traditional 401(k) contributions are generally made on a pre-tax basis. Qualified Roth withdrawals can generally be tax-free, while traditional 401(k) withdrawals are generally taxable.
2. Is a Roth 401(k) always better than a traditional 401(k)?
No. The better choice depends on your current tax rate, expected retirement tax rate, contribution strategy, income, and other financial circumstances. A Roth can be advantageous when paying taxes today is preferable to paying them later, while a traditional account can be valuable when the current tax deduction is particularly beneficial.
3. Why does the calculator ask for my current tax rate?
The calculator uses the current tax rate to estimate the after-tax employee contribution for the Roth scenario. This reflects the fact that Roth contributions are generally made after income taxes.
4. Why does the calculator ask for my retirement tax rate?
Traditional 401(k) withdrawals are generally taxable. The calculator uses your estimated retirement tax rate to convert the projected traditional balance into an estimated after-tax value.
5. Are Roth 401(k) withdrawals tax-free?
Qualified Roth 401(k) distributions can generally be tax-free, provided applicable requirements are met. Not every withdrawal is necessarily qualified, so actual tax treatment depends on the circumstances.
6. Does the employer match go into a Roth 401(k)?
Employer matching contributions have historically generally been made on a pre-tax basis, although plan rules can vary and tax law has evolved. Check your employer's current plan documents to determine how matching contributions are handled.
7. What investment return should I enter?
There is no guaranteed annual return. Use a reasonable long-term assumption and consider testing several rates. Running conservative, moderate, and optimistic scenarios can provide a better picture than relying on a single projection.
8. Why is salary growth included in the calculator?
If your contribution is based on a percentage of salary, increasing income can result in larger future contributions. Salary growth therefore can have a meaningful effect on your projected retirement balance.
9. Can I contribute to both a Roth 401(k) and traditional 401(k)?
Many employer plans allow employees to divide contributions between traditional and Roth 401(k) options, subject to applicable rules and plan provisions. Whether this is appropriate for you depends on your overall tax and retirement strategy.
10. Should I use this calculator to make my final retirement decision?
Use it as a planning aid rather than as personalized financial or tax advice. The results depend on assumptions about investment returns, salary growth, tax rates, contributions, and retirement timing. For a major retirement decision, consider reviewing your situation with a qualified financial or tax professional.
Final Thoughts
The decision between a Roth 401(k) and traditional 401(k) is fundamentally a decision about when you want to pay taxes.
A traditional 401(k) generally offers the potential for tax savings today, followed by taxable withdrawals later. A Roth 401(k) generally requires taxes to be paid on contributions today, while qualified withdrawals can potentially be tax-free.
The difference can become increasingly important as your retirement savings compound over many years.
Our Roth 401(k) vs 401(k) Calculator lets you compare these strategies using your age, retirement timeline, salary, contribution rate, employer match, expected investment return, tax rates, and salary growth. Most importantly, it compares estimated after-tax retirement values, giving you a more meaningful perspective than simply comparing account balances.
For the most useful analysis, try several scenarios rather than relying on a single result. Change the expected investment return, retirement tax rate, salary growth, contribution rate, and retirement age to see how sensitive your outcome is to different assumptions.
Ultimately, the best retirement strategy is one that fits your tax situation, investment plan, employer benefits, retirement goals, and long-term financial circumstances. Use the calculator to understand the trade-offs, then combine those estimates with your broader retirement plan before making important financial decisions.