How to Use a Roth IRA Calculator

Quick answer

What this calculator tells you

A Roth IRA calculator does two things a plain growth projection cannot. First it checks whether you can contribute at all, because Roth eligibility phases out as income rises. Then it projects how a balance plus annual contributions could grow — and because qualified Roth withdrawals are tax-free, that growth is not reduced by future tax.

This guide covers the 2026 contribution limit, the income phase-out that can shrink or block your contribution, and how the tax-free growth accumulates. Every example uses the calculator's default inputs, so you can open the tool and reproduce each figure.

Inputs that matter most

Start with documents rather than memory whenever possible. For this calculation, pay particular attention to:

• age and filing status
• modified adjusted gross income
• current balance and planned contribution
• years to grow and assumed return

Use values that describe the same point in time. Mixing an old balance with a new rate or an annual cost with a monthly figure can make a polished result unreliable.

When this calculator is most useful

Use this tool early enough to improve the decision, but late enough that the inputs are grounded in real information. It is particularly useful when:

• ✓You want to know whether your income lets you contribute to a Roth IRA, and how much.
• ✓You want to see what regular contributions could grow to over your working life.
• ✓You are near the income phase-out and want to see how much your allowed contribution shrinks.
• ✓You want to compare a Roth with a taxable account, where growth would be taxed.

It is less useful when the key facts are unknown, the options use different time periods, or the decision turns mainly on eligibility, contract language, taxes, or risks the calculator does not model. In those situations, gather the missing documents first and treat any early result as a rough range.

How the calculation works

The model turns the entered assumptions into a consistent comparison. It does not fill in facts that were not requested, predict changing markets, or reproduce an institution's underwriting system. That boundary matters: mathematical precision is not the same thing as certainty.

The 2026 contribution limit

The limit is the same whether the money goes to a Roth or a traditional IRA, and it covers all your IRAs together. For 2026, per the IRS:

• Under 50: $7,500.
• 50 or over: $8,600, which is $7,500 plus a $1,100 catch-up.

The calculator applies the figure for the age you enter and caps your contribution at it. It also caps the contribution at your taxable compensation, since you cannot contribute more than you earned. Contributions to other IRAs reduce the room that is left.

The income phase-out, and what it costs

This is the part a plain growth calculator leaves out. Roth eligibility falls as modified AGI rises through a band, then stops entirely. For a single filer in 2026 the band is $153,000 to $168,000:

• $100,000 modified AGI: below the range, full $7,500 allowed.
• $160,000: inside the range, capped at about $4,000.
• $170,000: above the range, $0 allowed directly.

For married filing jointly the band is higher, $242,000 to $252,000: at $200,000 the full amount is allowed, while at $247,000 the cap falls to about $3,750. The reduced contribution then feeds into the projection, so a return that looks modest may simply reflect a capped contribution rather than a low return.

Tax-free growth, and why time matters

Once eligibility is settled, the projection is a compounding calculation, with one crucial difference from a taxable account: the growth is not taxed on qualified withdrawal. On the default inputs:

• 20 years: balance about $384,860, of which $170,000 is contributions and about $214,860 is growth.
• 30 years: balance about $860,701, of which $245,000 is contributions and about $615,701 is growth.

Over the extra decade, contributions rise by $75,000 but the balance more than doubles, because growth compounds on a larger base and, in a Roth, is never reduced by tax. That tax treatment is the whole argument for the account: in a taxable account, the roughly $615,701 of growth would eventually be taxed, while in a Roth a qualified withdrawal keeps it in full.

Worked example

See the method in context

Take a 35-year-old single filer with $100,000 of modified AGI, a $20,000 Roth balance, contributing $7,500 a year for 30 years at a 7% return.

Because $100,000 is below the $153,000 phase-out, the full $7,500 is allowed. Over 30 years the balance grows to about $860,701. Contributions total $245,000 (the $20,000 start plus 30 years of $7,500), so about $615,701 is growth. In a Roth, qualified withdrawals of that whole amount are tax-free.

After running the base case, change one important input at a time. A less favorable rate, cost, return, income, or holding period shows whether the conclusion is sturdy or depends on a narrow set of assumptions.

Build three scenarios, not one prediction

A single answer can create false confidence. Three deliberately different cases reveal both the likely range and the assumptions that deserve more investigation.

Keep all unchanged inputs identical across the three runs. That discipline makes the comparison explainable and prevents several moving assumptions from hiding what actually changed the answer.

How to read the result

Look beyond the largest number on the screen. Review the breakdown, the time horizon, and any balance or cost that remains at the end of the comparison. Ask whether the result still fits cash flow and whether it changes under a conservative scenario.

Eligibility depends on your modified adjusted gross income, which can differ from your taxable income, and the projection assumes a steady return that real markets do not deliver. The right next step is to confirm your modified AGI and eligibility against current IRS guidance, then re-run the projection with a lower return.

Common mistakes to avoid

• Assuming you can always contribute. Above $168,000 of modified AGI, a single filer's direct Roth contribution is $0.
• Using taxable income for eligibility. The phase-out is based on modified AGI, which is usually higher.
• Contributing the limit to each IRA. The $7,500 is a combined limit across all your IRAs.
• Forgetting the catch-up. At 50 or over the 2026 limit is $8,600, not $7,500.
• Treating the growth as taxable. The point of a Roth is that qualified withdrawals, growth included, are tax-free.
• Using an optimistic return. At 5% instead of 7%, the default projection is about $276,000 lower.

Decision checklist

Before acting, work through these questions. A “no” does not automatically reject the option; it identifies where more evidence or a wider safety margin is needed.

1. 1Is my modified AGI below the phase-out for my filing status ($153,000 single, $242,000 married filing jointly in 2026)?
2. 2Am I contributing no more than the limit for my age ($7,500, or $8,600 at 50 and over)?
3. 3Do I have enough taxable compensation to support the contribution?
4. 4Have I accounted for any contributions to other IRAs, which share the same limit?
5. 5Do I understand the growth shown is tax-free only if withdrawals are qualified?

Key terms in plain English

Contribution limit

The most you can put into all your IRAs combined in a year: $7,500 for 2026, or $8,600 if you are 50 or over, which includes the $1,100 catch-up.

Modified AGI

Adjusted gross income with certain items added back. Roth eligibility is based on this figure, which can differ from your taxable income.

Phase-out range

The income band over which the allowed contribution falls from the full limit to zero. For 2026 it is $153,000 to $168,000 for single filers and $242,000 to $252,000 for married filing jointly.

Tax-free growth

Qualified Roth withdrawals, including all the growth, are not taxed. This is why the projected growth here is not reduced by future income tax the way a taxable account's would be.

Frequently asked questions