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
Current Savings & Investments ($)
$15,000
Annual Income ($)
$55,000
Annual Expenses ($)
50000
After entering these figures, review fire number, years to fire and fire age 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
FIRE Number
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.
Years to FIRE
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.
FIRE Age
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.
Savings Rate
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.
Current Progress
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 models your path to Financial Independence, Retire Early (FIRE) using a year-by-year compound growth simulation. Starting from your current savings balance, it adds your annual savings each year and applies your expected investment return until your portfolio reaches your FIRE number — defined as annual expenses divided by your safe withdrawal rate. The widely cited 4% rule, derived from the Trinity Study using historical US stock and bond data, suggests that a 25x expenses portfolio has historically survived 30-plus-year retirements. Many early retirees in the US choose a lower rate of 3% to 3.5% given longer time horizons and healthcare costs before Medicare eligibility at age 65.
The calculator does not account for taxes on investment withdrawals, inflation eroding purchasing power, Social Security income, or variable market returns. A 7% default return reflects approximate long-run US equity market performance after inflation. Your actual savings rate is calculated as annual savings divided by gross income, expressed as a percentage. Because this tool assumes a constant growth rate, real-world outcomes will vary — sequence-of-returns risk means that poor returns early in retirement can significantly shorten portfolio longevity even if long-run averages hold.
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
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
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