Coast Fire Calculator
Calculate your Coast FIRE number: the savings needed today so compound growth alone reaches your full FIRE target by retirement, with no additional
Coast Fire Calculator
Calculator
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Formula: Coast FIRE Number = Annual Expenses x 25 / (1 + real return)^years | Real Return = Nominal - Inflation
Worked example — Already Coast FIRE! Savings will grow to $1.6M+
Formula
Coast FIRE Number = Annual Expenses x 25 / (1 + real return)^years | Real Return = Nominal - Inflation
Coast FIRE is when your current savings, growing at the expected return rate, will reach your FIRE number by retirement without additional contributions. FIRE number = 25x annual expenses (4% rule).
Worked Examples
Example 1: $150K at age 30
Problem:$150K savings, age 30, retire at 65, $50K/yr expenses, 7% return
Solution:FIRE number: $1.25M. Coast number: $1.25M/(1.07)^35 = $116,720. $150K > $116,720
Result:Already Coast FIRE! Savings will grow to $1.6M+
Frequently Asked Questions
What is Coast FIRE?
Coast FIRE means you have enough invested that, even without further contributions, compound growth will reach your full FIRE number by retirement. You still need to cover current expenses but can stop actively saving.
What is the 4% rule?
The 4% rule (Trinity study) suggests you can withdraw 4% of your portfolio annually in retirement with low risk of running out over 30 years. FIRE number = annual expenses x 25 (which is 1/0.04).
How is Coast FIRE different from Lean FIRE, Fat FIRE, and Barista FIRE?
These are all variations of the Financial Independence Retire Early (FIRE) movement with different portfolio and income requirements. Lean FIRE means fully retiring on a minimal budget (typically under $40,000 per year). Fat FIRE means fully retiring with a comfortable or luxurious budget (often $80,000 or more per year). Barista FIRE means semi-retiring and working part-time to cover current expenses while a smaller portfolio grows. Coast FIRE is a milestone status, not a retirement style — it means your current portfolio will reach your FIRE number by retirement age without additional contributions, though you still work to cover living costs.
Is a 7% real return assumption realistic for Coast FIRE calculations?
The historical real return (after inflation) of the US stock market has averaged approximately 7% per year over long periods based on S&P 500 data. However, this is not guaranteed and past returns do not predict future results. During any specific 20-35 year period, returns can be significantly higher or lower. Many financial planners use a more conservative 5-6% real return for long-range planning to provide a safety margin. The sequence-of-returns risk (getting poor returns early in your accumulation phase) also matters. Using a lower return assumption provides a buffer against underperformance.
What is the difference between the Coast FIRE number and the FIRE number?
The FIRE number is the portfolio you need on the day you stop working, conventionally 25 times annual expenses. The Coast FIRE number is that same target discounted back to today at your expected real return: FIRE number divided by (1 plus r) to the power of the years remaining. It is the amount that, left alone, compounds into the full target by itself. Reaching it does not mean you can stop working - it means you can stop adding to investments.
How should inflation affect the return rate I enter here?
The discounting uses whatever return you type in the return field, so the two sides of the calculation must be in the same units. If your annual expense figure is stated in today's spending power, the rate you enter should be a real return - your expected nominal return less expected inflation - because 50,000 dollars of spending will cost far more in nominal dollars decades from now. If instead you inflate the expense target to future dollars yourself, enter the nominal return. Mixing the two understates the Coast number.
How much does changing my target retirement age move the Coast number?
Dramatically, because the discounting is exponential. Each additional year divides the requirement by one plus the real return. At 7 percent real, ten extra years divides it by 1.07 to the tenth, which is about 1.97 - so retiring at 65 instead of 55 nearly halves the amount you need invested today. That sensitivity cuts both ways: pulling the target date closer raises the Coast number sharply, which is why the retirement age input deserves as much thought as the return assumption.
If I have reached Coast FIRE, should I stop investing entirely?
The calculation says you may, but it rests on assumptions that could disappoint - the real return, the expense target and the retirement date are all estimates over decades. Treating Coast FIRE as permission to reduce saving rather than eliminate it preserves a buffer against a weak return sequence or a lifestyle that grows. Many people use the milestone to justify a lower-paying but better job, cutting contributions rather than stopping them, and recheck the number annually against the actual balance.
How does the 25x multiple change for a very early retirement?
The 4 percent guideline, and therefore the 25 times multiple, came from studies of 30-year retirement horizons. A retirement beginning in your forties could last 50 years or more, which raises the probability that an unlucky return sequence exhausts the portfolio. Planners addressing that commonly use 3 to 3.5 percent instead, implying a multiple of roughly 28 to 33 times expenses. Raising the multiple raises both the FIRE number and, proportionally, the Coast number you need today.
Does the Coast FIRE number account for Social Security or a pension?
No. The standard calculation assumes the portfolio funds all expenses, which is deliberately conservative. Any future income stream - Social Security, a defined-benefit pension, rental income, an annuity - reduces the portfolio required, because you only need to cover expenses net of that income. Some people model it by subtracting expected annual benefits from expenses before applying the multiple. Given how far away those entitlements are for an early-career saver, ignoring them builds in a useful margin of safety.
References
Reviewed for accuracy by Sahil, Senior Finance & Tax Editor · Editorial policy
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