Coast FIRE Calculator

Find the amount that may be able to coast

Coast FIRE separates two dates: the date retirement saving may become optional and the date portfolio withdrawals begin. Existing savings remain invested between them.

First, the calculator estimates a FIRE number in today’s dollars:

FIRE number today = annual retirement spending ÷ withdrawal rate

At $60,000 of annual spending and a 4% withdrawal assumption, the target is $1.5 million in today’s dollars. Inflation then grows that amount to the retirement date.

The Coast number discounts the future target back to today using the expected nominal investment return:

Coast number today = future retirement target ÷ (1 + return)ʸᵉᵃʳˢ

If current invested retirement savings meet or exceed that number, the scenario is labeled Coast FIRE reached.

A worked scenario

For age 30, retirement at 65, $60,000 of annual spending, a 4% withdrawal rate, 7% nominal return, and 3% inflation, the future target is larger than $1.5 million because it is stated in age-65 dollars. Discounting that future target by 35 years of assumed 7% growth produces the amount required today.

With $150,000 currently invested, the default scenario still shows a gap. Raising current savings, delaying retirement, lowering spending, increasing the withdrawal assumption, or assuming a higher return can reduce it—but each change carries a different practical risk.

Use real return as a reasonableness check

Nominal return and inflation should not be selected independently without thought. A 7% return and 3% inflation imply an exact real return of roughly 3.88%, not a guaranteed 4%. Investment fees reduce the return reaching the portfolio, which is why the investment fee calculator is a useful companion.

Run conservative cases with lower return and higher inflation. Also test retirement spending above the first estimate. A plan that only works with optimistic inputs is not a robust Coast plan.

Coast FIRE does not remove retirement risk

Stopping contributions removes a safety margin. Market returns arrive unevenly, and early poor returns can leave the portfolio below its path. Life events, health costs, taxes, job changes, retirement timing, and spending needs can change the target.

Continue monitoring the result at least annually. Coast FIRE can support a choice to work fewer hours, change careers, or redirect savings, but it is not a legal or financial status.

Compare the traditional FIRE calculator for a continuing-contribution path and the retirement calculator for salary-based saving and employer match.

Model limitations

The calculation assumes constant annual returns and inflation, end-date retirement, no taxes or fees, no pension or Social Security, and a fixed spending target. It does not model sequence-of-returns risk or portfolio allocation. Results are educational projections, not investment advice or a guarantee of retirement security.