Coast FIRE Calculator

Frequently Asked Questions

What is Coast FIRE?

Coast FIRE is the balance at which your invested assets, with no further contributions, are projected to grow to your full FIRE number by traditional retirement. You still work and cover living expenses, but you no longer have to save. This is general education, not financial advice.

How is the Coast FIRE number calculated?

Required FIRE number = annual expenses ÷ safe withdrawal rate (often 4%, i.e. expenses × 25). Required balance today = FIRE number ÷ (1 + r)^years, where r is the real annual return and years is time to retirement. At r = 5% real over 25 years, $1M needed becomes ~$295k today.

What return assumption is reasonable?

A real (inflation-adjusted) return of 4–6% on a diversified stock-heavy portfolio is a commonly used long-term planning figure, though future returns are not guaranteed. Lower assumptions raise the Coast FIRE balance you need.

How is Coast FIRE different from regular FIRE?

Regular FIRE means having enough invested to fully retire now. Coast FIRE means having enough that compound growth alone will get you there by a set future date - you can stop saving, downshift careers, or take a lower-paying job that just covers expenses. This is informational only.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Coast FIRE is the moment your already-invested savings are large enough that, with zero further contributions, normal market growth alone will carry the balance to your full retirement target by the year you plan to stop working. This tool takes your current invested balance, the real (inflation-adjusted) return you expect, the number of years until retirement, and your target annual spending, then compounds the balance forward with no new deposits. It compares that projected future value against your FIRE number - annual expenses divided by your chosen safe withdrawal rate (a 4% rate is the classic 25×-expenses rule). Because the calculation uses a real return, the answer is already in today's dollars, so you do not have to separately inflate your spending. The headline output is the "Coast FIRE number today": the smallest balance you would need right now so that growth alone closes the gap. Reaching it means you can, in principle, stop retirement saving entirely and merely cover current living costs - the portfolio coasts the rest of the way on its own.

Formula / Method

Two equations drive the result. First the target: FIRE number = annual expenses × (100 ÷ SWR), so 4% gives 25× expenses and 3.5% gives roughly 28.6×. Second the projection: future value = balance × (1 + r)^years, where r is the real return as a decimal. The Coast FIRE number you need today is the target discounted back: FIRE number ÷ (1 + r)^years. If your present balance is at or above that discounted figure, future value will meet or exceed the target and you have coasted. Progress is simply current balance ÷ coast number. Blank, zero, or negative entries for expenses, years, or withdrawal rate are rejected so the projection never returns NaN, and a zero balance is allowed because a brand-new saver legitimately has nothing invested yet.

Worked Example

Suppose you have $120,000 invested, expect a 5% real return, plan to retire in 25 years, spend $50,000 a year, and use a 4% withdrawal rate. The FIRE number is 50,000 × 25 = $1,250,000. The coast number today is 1,250,000 ÷ 1.05²⁵ ≈ 1,250,000 ÷ 3.386 ≈ $369,100 - so $120,000 is about 33% of the way there, not yet coasting. Run it again with $400,000 invested: future value is 400,000 × 3.386 ≈ $1,354,500, comfortably past the $1.25M target, so contributions become optional and the surplus is roughly $104,500 in today's dollars.

Common Mistakes

Entering a nominal return (e.g. 8%) instead of a real return (e.g. 5%) - that overstates future value and makes Coast FIRE look closer than it is.

Forgetting that "coasting" still requires income to cover today's living expenses; it only means you stop retirement saving, not that you stop working.

Treating the 4% rule as a guarantee - it is a historical heuristic, and a lower withdrawal rate raises the target substantially.

Ignoring taxes and fees, which quietly erode the real return; shave your assumed return to stay conservative.

Assuming a smooth annual return when real markets are volatile; an early bad stretch can derail a thin coast cushion.

Tips & FAQ

Is Coast FIRE the same as being retired? No - it means your invested money no longer needs feeding, but you still earn enough to live on until withdrawals begin. What return should I use? Many planners use a 4–6% real return for a stock-heavy portfolio; lower if you hold more bonds or want a safety margin. Why does a smaller withdrawal rate raise my target so much? Because the target is the reciprocal of the rate: 4% means 25×, but 3% means about 33× expenses. Should I really stop contributing once I coast? Most people keep saving anyway for an earlier exit or a bigger cushion; Coast FIRE is a milestone, not a mandate. This tool is educational and not financial advice; verify assumptions with a qualified planner before changing your savings plan.

Frequently Asked Questions

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