Rates & sources
Compound growth assumes reinvested returns and no platform fees. Past performance is not a guide to future returns.
Source: FCA — Investment basics — figures refreshed at the start of each tax year.
When to use this calculator
- Before choosing between saving, investing, or increasing your monthly contribution.
- When you want to compare best-case, base-case, and cautious return assumptions.
- When you need a quick projection before making a longer-term portfolio decision.
- When you are deciding how many more years of contributions are needed to reach a specific target balance.
- When you want to see whether starting earlier versus contributing more each month produces a bigger outcome.
A realistic US planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Your Current Age
35
Retirement Age
35
Current Roth IRA Balance ($)
$1,400
Annual Contribution ($)
$250 per month
After entering these figures, review tax-free balance, your contributions and tax-free growth together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Tax-Free Balance
Review this figure alongside your gross income so you can understand the true cost of deductions and plan around any thresholds before the tax year closes. If the figure looks higher than expected, check whether any pension or gift-aid contributions could reduce your taxable income.
Your Contributions
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Tax-Free Growth
Review this figure alongside your gross income so you can understand the true cost of deductions and plan around any thresholds before the tax year closes. If the figure looks higher than expected, check whether any pension or gift-aid contributions could reduce your taxable income.
Traditional IRA Equivalent
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
4% Rule Monthly
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This calculator projects your Roth IRA balance at retirement using compound annual growth, capped at the 2024 IRS contribution limits of $7,000 ($8,000 for ages 50 and over). Each year, your contribution is added to the running balance and the full sum grows at your chosen rate. The Traditional IRA equivalent divides your Roth balance by one minus your marginal tax rate, showing the pre-tax account value that delivers the same after-tax spending power — quantifying Roth’s tax-free advantage in concrete dollar terms.
Results are illustrative and assume a constant annual return with contributions made at the start of each year. They do not account for income phase-outs, backdoor conversions, Roth 401(k) rollovers, or required minimum distributions, which do not apply to Roth IRAs under current law. Contribution limits and tax rates are subject to change by Congress. Verify current IRS limits at irs.gov and consult a financial advisor before making contribution or conversion decisions.
Common mistakes
- !Assuming a constant return without checking a more conservative growth rate.
- !Forgetting to include ongoing contributions, fees, or tax wrappers where relevant.
- !Focusing only on the final balance instead of the path required to reach it.
- !Ignoring the drag of platform fees or fund charges, which can reduce the real compounded return significantly over ten or more years.
- !Comparing ISA and general investment account projections without adjusting for the tax treatment of interest, dividends, or capital gains.
What to do next
- Test a cautious, expected, and optimistic growth rate instead of relying on a single projection.
- Compare this result with related savings or retirement tools before committing more money.
- Use the linked guides to understand which assumptions matter most over longer periods.
- Consider running the same figures in an ISA and a general account scenario to see how the tax treatment changes the outcome over ten or more years.
- If the projected balance falls short of your target, use the tool to work backwards — increase the monthly contribution until the result meets your goal.
Frequently asked
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End-of-article next steps
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