Roth vs Traditional IRA Calculator

How this Roth vs Traditional IRA calculator works

This Roth vs Traditional IRA calculator starts from a single pre-tax savings budget and then applies taxes in different places for each account type.

• Roth scenario: You pay your current marginal tax rate before the money enters the Roth IRA. Only the after-tax portion is invested, but qualified withdrawals can later come out tax-free.
• Traditional scenario: The full pre-tax budget is invested in a Traditional IRA. The tax benefit arrives now, but retirement withdrawals are modeled at your expected retirement tax rate.

The calculator assumes the same contribution amount every year, that the balance compounds at a constant annual rate of return, and that taxes are applied either up front for Roth or at the end for Traditional, but not in between. That keeps the comparison clean and makes it easier to see how tax timing interacts with growth.

Core Roth vs Traditional IRA formulas

Both paths use the future value of an ordinary annuity because the calculator assumes the same yearly contribution pattern for Roth and Traditional. What changes is the amount that actually reaches the Roth account and the tax applied to the Traditional balance at the end.

Where:

• P = annual contribution actually deposited in the account
• r = annual rate of return as a decimal, so 7% = 0.07
• n = number of years you contribute and invest

The calculator uses this formula twice, once for Roth and once for Traditional, with different effective contributions.

Roth IRA Calculation

Let C be your annual pre-tax contribution budget and t_now be your current marginal tax rate as a decimal. Because Roth contributions are made with after-tax dollars, the amount that actually lands in the Roth account each year is:

PRoth = C × (1 − tnow)

The future value of the Roth account at retirement is then:

FVRoth = PRoth × ((1 + r)n − 1) / r

Under standard rules for qualified withdrawals, this Roth future value is already after-tax, because income tax was paid before the money entered the account.

Traditional IRA Calculation

For the Traditional IRA, your entire pre-tax budget is contributed:

PTrad = C

The pre-tax future value is:

FVTrad, pre-tax = PTrad × ((1 + r)n − 1) / r

Let t_ret be your expected retirement marginal tax rate. To estimate the spendable value after tax in retirement, the calculator multiplies by (1 − t_ret):

In simpler text form:

FVTrad, after = FVTrad, pre-tax × (1 − tret)

One practical insight falls straight out of the Roth vs Traditional IRA formulas. When the same pre-tax savings budget is used and the growth assumption is identical, the tax-rate relationship often matters more than the return rate does. Return and time still make the balances larger, but the comparison between your current tax rate and your retirement tax rate usually decides which account leaves you with more spendable money.

Interpreting Your Roth vs Traditional IRA results

After you run this Roth vs Traditional IRA calculator, the two values you care about are the spendable Roth balance and the spendable Traditional balance at the end of the chosen time horizon. Here is how to read the result:

• If the Roth after-tax value is higher, then under your assumptions it is better to pay tax now and let the money grow tax-free in retirement.
• If the Traditional after-tax value is higher, then under your assumptions it is better to take the tax benefit today and pay tax later at the retirement rate you entered.
• If the values are very close, then minor changes in tax rates, return assumptions, or contribution timing could flip the winner. In that case, tax diversification may be more useful than trying to force one side to dominate.

The biggest driver in a Roth vs Traditional IRA decision is usually the gap between your current and retirement tax rates:

• Higher tax rate now than in retirement: A Traditional IRA is often favored because you avoid a higher tax bill today and pay a lower rate later.
• Lower tax rate now than in retirement: A Roth IRA often looks better because you lock in the lower rate now and avoid higher taxes on withdrawals later.

The rate of return and years to invest still matter, because they determine how much the account grows before taxes are considered. But when the same pre-tax contribution budget is applied to both paths, the tax comparison usually does the heavy lifting. A longer horizon magnifies the dollars involved, while a shorter horizon makes the difference smaller without changing the underlying logic of pay now versus pay later.

Worked Example: Roth vs Traditional IRA over 30 years

This Roth vs Traditional IRA worked example uses the same kind of inputs you would enter into the calculator and shows how a lower retirement tax rate can make the Traditional side edge ahead even when the Roth contribution feels simpler.

• Annual contribution pre-tax C = $6,000
• Current tax rate t_now = 24% or 0.24
• Retirement tax rate t_ret = 22% or 0.22
• Annual return rate r = 7% or 0.07
• Years to invest n = 30

Roth Scenario

After-tax contribution each year:

PRoth = 6,000 × (1 − 0.24) = 6,000 × 0.76 = 4,560

Future value:

FVRoth = 4,560 × ((1.07)30 − 1) / 0.07

Numerically, ((1.07)³⁰ − 1) / 0.07 is about 94.46, so:

FVRoth ≈ 4,560 × 94.46 ≈ $430,700 rounded

Because this is a Roth IRA, we treat the $430,700 as fully spendable in retirement under current qualified withdrawal rules.

Traditional Scenario

Annual contribution:

PTrad = 6,000

Future value before tax:

FVTrad, pre-tax = 6,000 × ((1.07)30 − 1) / 0.07

Using the same factor of about 94.46:

FVTrad, pre-tax ≈ 6,000 × 94.46 ≈ $566,800 rounded

After applying the retirement tax rate of 22%:

FVTrad, after = 566,800 × (1 − 0.22) = 566,800 × 0.78 ≈ $442,100

In this Roth vs Traditional IRA example, the Traditional side finishes at an estimated $442,100 after tax, slightly higher than the Roth value of $430,700. That difference comes from the assumption that your retirement tax rate is lower than your current rate. If you changed the retirement tax rate upward, the Roth result would often become the stronger one. The example also shows why the gross Traditional balance can be misleading: the pre-tax account looks much larger before taxes are applied, but the real comparison is the amount you can actually spend.

When Roth vs Traditional IRA may be better

In a Roth vs Traditional IRA decision, the calculator output is only part of the picture. The table below groups a few common planning situations that often push the math toward one side or the other when the pre-tax cost to you is the same.

In practice, many savers use both account types across their careers to build tax flexibility in retirement. That approach can reduce the risk of guessing wrong about future tax law or future income. This calculator does not tell you that one account is universally superior. It helps you see how different assumptions tilt the math, so you can decide whether a pure Roth strategy, a pure Traditional strategy, or a blended approach fits your situation best.

Roth vs Traditional IRA assumptions and limitations

Because a Roth vs Traditional IRA comparison depends on when tax is paid, this calculator uses a simplified model to keep the math transparent and easy to check.

• Constant tax rates: The calculator assumes your current and retirement tax rates remain fixed at the percentages you enter. In reality, tax brackets can change due to legislation, inflation adjustments, or shifts in your income.
• Single marginal rate: It models tax impact using a single marginal rate, not a full graduated tax bracket system.
• Constant annual return: Investment returns are assumed to be the same every year. Real markets fluctuate, and sequence-of-returns risk is not modeled.
• End-of-year contributions: Contributions are treated as if made at the end of each year. Contributing more frequently or earlier in the year would slightly change the actual growth.
• No IRS contribution limits: The tool does not enforce annual IRA contribution limits or income-based eligibility rules. In reality, your ability to contribute may be capped or restricted.
• No penalties or special rules: Early-withdrawal penalties, exceptions, and the five-year rules for Roth IRAs are ignored.
• No state or local taxes: Only a single combined tax rate is modeled. State and local income taxes, along with other levies, are not separately accounted for.
• Required minimum distributions: The complexities of RMDs for Traditional IRAs and the absence of lifetime RMDs for Roth IRAs under current rules are not modeled explicitly.
• Inflation not modeled separately: The calculator uses nominal dollar amounts and nominal rates of return. It does not adjust for purchasing power.
• No interaction with other accounts: Employer plans like 401(k)s, SIMPLE IRAs, pensions, and Social Security are not integrated into the projection.

Because of these limitations, the outputs should be viewed as illustrative estimates rather than precise forecasts. They are most useful when you compare scenarios. For example, you might enter one retirement tax rate, then rerun the numbers with a higher or lower rate to see how sensitive the answer is. That habit is often more useful than treating one single output as final.

This calculator and explanation are for educational purposes only and do not constitute tax, legal, or investment advice. Individual situations vary, and tax laws change. Before making decisions about IRA contributions, conversions, or withdrawals, consider speaking with a qualified financial or tax professional who can evaluate your specific circumstances.