This Coast FIRE calculator estimates whether the investments you already have could grow into a future retirement target by your chosen age. It works backwards from annual retirement spending and a withdrawal-rate assumption, then compares that target with your current invested pot. The result is educational only, not a prediction or financial advice. Small changes to age, return, inflation, fees or spending can materially change the answer. Investments can fall as well as rise, past performance is not a guide to future results and capital is at risk.
What this calculator assumes
- The calculator uses illustrative return, inflation, fee and withdrawal-rate assumptions.
- Figures are simplified into today’s money so the target is easier to compare.
- Monthly contributions are optional and are shown as part of the projection, not as a recommendation.
- Investment values can go down as well as up and capital is at risk.
How to read the Coast FIRE number
The Coast FIRE number is the estimated amount you would need invested today for that pot to grow towards your target retirement pot by the age you enter, assuming no further contributions are needed. If your current pot is above that number, the calculator will show that it is above the estimate. If it is below, the current gap shows how much more would be needed on these assumptions. This is a planning illustration, not a retirement plan, because future returns, costs and personal spending can all change.
Spending, withdrawal rates and target pots
The estimated FIRE target is based on the annual retirement spending you enter and the withdrawal-rate assumption. A lower withdrawal rate creates a larger target pot, while a higher withdrawal rate creates a smaller one. Neither is automatically right. Real retirement planning can also involve pensions, tax, cash buffers, state pension entitlement, mortgage costs and changing spending patterns. This calculator keeps those details deliberately simple so you can see the relationship between spending, time and compounding before adding more personal layers.
Inflation, fees and real returns
The calculator uses a simplified real return by subtracting fees and inflation from the annual return assumption. That keeps the figures closer to today’s money, which makes the target easier to compare with your current spending. It is still only a simplification. Market returns are not smooth, inflation changes over time and fees can vary by account or investment product. The most useful way to use the tool is to test several scenarios and notice how sensitive the result is to the assumptions.
Useful official sources
FAQs
What does Coast FIRE mean?
Coast FIRE is the idea that an invested pot may already be large enough to grow towards a future retirement target without needing further retirement contributions, assuming there is enough time and the investment assumptions hold.
Is the withdrawal rate a safe amount to use?
No single withdrawal rate is guaranteed. The rate is an assumption used to turn annual retirement spending into an estimated target pot, and different assumptions can produce very different results.
Why does inflation change the result?
Inflation affects spending power. This calculator subtracts inflation from the return assumption so the result is easier to read in today’s money, but real inflation will not be smooth or predictable.