About the Roth IRA Calculator
A Roth IRA's biggest advantage is simple: every dollar it grows to is completely tax-free at withdrawal in retirement, since you contribute with after-tax money today. Our Roth IRA Calculator projects that tax-free growth from your current balance and contributions.
How It Works
The calculator compounds your current balance and adds your monthly contribution each period at your expected rate of return, growing the balance over your chosen number of years - the exact same math as any compound growth projection, but the resulting balance is entirely tax-free when withdrawn under Roth IRA rules.
Formula & Methodology
The growth math itself is identical to any other compound-interest-plus-contributions projection - what makes a Roth IRA different is entirely a tax rule, not a different formula. Because contributions are made with money that's already been taxed, the IRS never taxes the account again, meaning the full projected balance (contributions plus every dollar of growth) is what you actually get to keep and spend, unlike a pre-tax account where a portion of the balance effectively belongs to the IRS.
Step-by-Step: Calculating It By Hand
- 1Convert your expected annual rate of return to a monthly rate.
- 2Compound your current balance forward using that monthly rate over your investing horizon.
- 3Add the compounded value of monthly contributions using the annuity growth formula.
- 4The resulting total is your projected balance, fully available tax-free at qualified withdrawal.
Examples
Long time horizon
$10,000 currently saved plus $500/month at a 7% expected return over 30 years grows to a substantial, entirely tax-free balance at retirement.
Value of tax-free growth
Compare this to a Traditional IRA's after-tax value (see our Traditional IRA Calculator) - a Roth's full balance is available at withdrawal, with nothing owed to the IRS.
Advantages
- Models the full, untaxed value of Roth IRA growth
- Useful for comparing against a Traditional IRA's after-tax equivalent
- Shows the split between contributions and investment growth clearly
- Simple enough to test different contribution levels quickly
Common Mistakes
- Forgetting Roth IRA contributions have annual IRS limits and income eligibility phase-outs this simplified projection doesn't enforce
- Assuming a flat rate of return every year rather than realistic market variability
- Not comparing against a Traditional IRA, since the better choice depends on your current versus expected future tax rate
- Overlooking that Roth contributions (not earnings) can typically be withdrawn penalty-free before retirement, unlike a Traditional IRA
Edge Cases to Watch For
- Roth IRA contributions are subject to annual IRS dollar limits and phase out entirely above certain income thresholds, neither of which this simplified projection enforces.
- Contributed principal (not earnings) can generally be withdrawn at any time without tax or penalty, a flexibility unique to Roth accounts among retirement vehicles.
- Qualified withdrawals require both reaching age 59½ and the account being open at least five years - withdrawing earnings before meeting both conditions can trigger taxes and penalties.
- A backdoor Roth conversion strategy lets high earners who exceed the direct contribution limit still get money into a Roth, though that process has its own tax nuances this calculator doesn't model.
Common Use Cases
- Projecting tax-free retirement savings growth
- Comparing a Roth IRA against a Traditional IRA for your specific tax situation
- Planning contribution amounts to reach a retirement goal
- Understanding the long-term value of tax-free compounding