What is the difference between Coast FIRE and traditional FIRE?

Traditional FIRE means you have 25x your annual expenses saved — enough to retire today. Coast FIRE means you have enough invested right now that compound interest alone carries you to that same 25x number by retirement age. At 30 years old with $50K/year spending, traditional FIRE requires $1.25 million. Coast FIRE requires about $117,000. Same end result. Very different starting lines.

How accurate is the Coast FIRE calculator?

The formula is exact: Coast Number = FIRE Number / (1 + real return)^years. The calculator shows three scenarios (5%, 7%, 8% real return). The 7% baseline reflects 90 years of S&P 500 data. The conservative 5% scenario has been true in virtually every 30-year rolling period in recorded market history.

What investment return should I use?

7% real return (after inflation) is the historical average for a broad US stock market index fund from 1926 to today. If you hold bonds or cash, dial it down to 5-6%. If your investment fees are above 0.2%, subtract those too — a 0.5% fee on a 30-year timeline costs roughly $150,000 on a $1.25M target. The calculator lets you adjust all of these in Advanced Settings.

What is the safe withdrawal rate (SWR)?

The 4% rule comes from the Trinity Study (Cooley, Hubbard & Walz, 1998). They tested every possible 30-year retirement window from 1926 to 1995 using a 50/50 stock/bond portfolio. In 95% of cases, a 4% withdrawal rate did not run out of money. The calculator defaults to 4%. For a safety margin, 3.5% works too — it raises your FIRE Number from 25x to about 29x annual expenses.

Does Coast FIRE account for taxes?

Not directly. The Coast FIRE number is a pre-tax portfolio target. In retirement, your actual spending power depends on which accounts your money lives in — Roth IRAs withdraw tax-free, Traditional 401(k)s are taxed as income, and taxable brokerage accounts get capital gains treatment. A reasonable rule of thumb: if most of your money is in tax-deferred accounts, add 15-20% to your Coast Number.

What happens if the market crashes after I hit Coast FIRE?

A crash hurts but does not break the math if you have time. A 35-year-old who hits Coast FIRE and watches the market drop 30% still has 30 years until retirement. Historically, the S&P 500 has recovered from every major crash within 3-7 years. The Trinity Study itself included the 1929 crash, the 1973-74 bear market, and the 1987 Black Monday — and the 4% rule still held.

How often should I recalculate my Coast FIRE number?

Once a year, or whenever your life changes in a way that moves your spending or income by 10%+. The Coast Number is not a moving target that needs daily monitoring. It is a checkpoint. Calculate it, write it down, check back in 12 months.

Is Coast FIRE right for me?

If you earn an income, spend less than you make, and invest the difference in index funds — Coast FIRE is a math problem with a specific solution. A 30-year-old earning $60K who saves $1,000/month crosses the Coast Threshold in about 5 years. The question is not whether Coast FIRE works. The question is whether you have run your numbers yet.

Coast FIRE Calculator

Find your Coast Number in 60 seconds

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How to Use This Calculator

Enter your age•Set retirement goal•Get your Coast FIRE number!

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Adjust values to see your Coast FIRE number update in real-time

Age Settings

Your current age and target retirement age

Current Age

Retirement Age

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Your spending, assets, and contributions

Annual Spending in Retirement

$20k$200k

Current Assets

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Monthly Contribution

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Adjust the sliders to see how your Coast FIRE number changes in real-time. Open Advanced Settings to customize return rates and inflation for a personalized estimate.

Your Coast FIRE Number

Not Started

Invest this amount today to retire comfortably

Coast FIRE Number

$164,209

Invest this amount today, and you're set for retirement

FIRE Number

$1,250,000

Progress to Coast FIRE0.0%

Start investing to track your progress

Key Metrics

Years to Retirement

Real Return

7.00%

Current Assets

FIRE Progress

0.0%

With Monthly Contributions

Projected at Retirement

$1,133,529

Years to Coast FIRE

On Track to FIRE

Not Yet

Monthly Contribution

$1,000

Coast FIRE by Age

Reference table showing how much you need invested at different ages to reach Coast FIRE (assuming $50k annual spending, 65 retirement, 7% real return)

Age	Years to Retirement	Coast Number	Monthly Investment
25	40 years	$83,000	$200
30	35 years	$117,000	$300
35 You	30 years	$164,000	$500
40	25 years	$230,000	$800
45	20 years	$323,000	$1,300
50	15 years	$453,000	$2,500
55	10 years	$635,000	$5,300
60	5 years	$891,000	$14,900

40 years to go

Coast Number:$83,000

Monthly:$200

35 years to go

Coast Number:$117,000

Monthly:$300

You

30 years to go

Coast Number:$164,000

Monthly:$500

25 years to go

Coast Number:$230,000

Monthly:$800

20 years to go

Coast Number:$323,000

Monthly:$1,300

15 years to go

Coast Number:$453,000

Monthly:$2,500

10 years to go

Coast Number:$635,000

Monthly:$5,300

5 years to go

Coast Number:$891,000

Monthly:$14,900

How to use this table: Find your current age to see how much you need to invest today to reach Coast FIRE. The "Monthly Investment" column shows how much you need to save each month from now until retirement to reach your Coast Number.

Note: This table assumes a 7% real investment return (after inflation) and 4% safe withdrawal rate. Your actual numbers may vary based on market conditions and your personal circumstances.

Your Age (35): You're in the prime building years. Keep saving and investing!

What Does Coast FIRE Mean?

Coast FIRE means you have reached the point where your existing investments, left alone, will compound into your full retirement fund by the time you need them. No more contributions required. You are done saving.

This is The Coast Threshold — the moment your money starts working harder than you do. Once you cross it, every dollar you earn from that point forward is optional. You can keep your job, quit your job, switch to part-time, or start a business. Your retirement is already locked in.

The math behind it is straightforward. If you need $1,250,000 to retire (using The 25x Rule at $50,000/year spending and a 4% withdrawal rate), and you have 30 years until retirement, a 7% real return means you only need about $164,200 invested today. That $164,200 compounds at 7% annually and arrives at $1.25 million without a single additional deposit.

Unlike traditional FIRE, which requires your full FIRE Number saved before you stop working, Coast FIRE gives you the option to redirect your income elsewhere — a career change, more time with family, or simply working less. The retirement math is already handled.

→ Full explanation: What is Coast FIRE?

What Is Your Coast FIRE Number?

Your Coast FIRE number is the exact amount you need invested today so that compound interest finishes the job without another dollar from you.

The calculation is two formulas:

Step 1 — Your FIRE Number:

FIRE Number = Annual Spending ÷ Safe Withdrawal Rate

At $50,000/year spending with a 4% SWR: $50,000 ÷ 0.04 = $1,250,000

Step 2 — Your Coast FIRE Number:

Coast Number = FIRE Number ÷ (1 + Real Return Rate)^{Years to Retirement}

For a 35-year-old targeting retirement at 65, using 7% real returns:

$1,250,000 ÷ (1.07)³⁰ = $164,200

At $164,200 invested, you have crossed The Coast Threshold. Every year from now, that money grows by roughly 7% in real terms. After 30 years, it reaches $1,250,000. You never added another cent.

The inputs are adjustable — your spending, return rate, and retirement age all change the number. But the formula does not. The 4% Safe Withdrawal Rate comes from the Trinity Study (Cooley, Hubbard & Walz, 1998). The 7% real return reflects long-run S&P 500 performance after inflation.

Coast FIRE Number by Age

Your Coast FIRE number depends heavily on how much time you give compound interest. A 25-year-old needs less than half of what a 45-year-old needs to reach the same retirement target.

Here are the numbers for $50,000/year in spending, a 4% Safe Withdrawal Rate, 7% real returns, and retirement at 65:

Age	Years to 65	Coast FIRE Number
25	40	$83,500
30	35	$117,100
35	30	$164,200
40	25	$230,300
45	20	$323,000
50	15	$453,100
55	10	$635,400

The difference between starting at 25 and starting at 35 is not 10% or 20%. It is nearly double. That is The Compounding Gap at work — the gap between what time does for you and what time does to you.

Every decade you wait, the required Coast Number roughly doubles. A 25-year-old with $83,500 invested is in the same position as a 45-year-old with $323,000. Same retirement outcome. Different starting line.

→ See Coast FIRE numbers for your exact age and spending level: Coast FIRE Number by Age

Assumes $50,000/year spending, 4% SWR (Trinity Study), 7% real return, retirement at 65. Last reviewed: April 2026

Three People, Three Numbers

The math is the same for everyone. The inputs change. Here are three people at different starting points — and what Coast FIRE looks like for each of them.

Sarah, 28 — $62,000 invested

$45,000/year spending, plans to retire at 65, 7% real return

FIRE Number = $45,000 / 0.04 = $1,125,000

Coast Number = $1,125,000 / (1.07)³⁷ = $89,200

Sarah has $62K. Her Coast Number is $89K. She is 70% of the way there. At her current savings rate of $1,200/month, she will cross the Coast Threshold in about 2 years — at age 30. After that, every dollar she earns is optional income. Her retirement is already mathematically on track.

Marcus, 38 — $95,000 invested

$55,000/year spending, plans to retire at 65, 7% real return

FIRE Number = $55,000 / 0.04 = $1,375,000

Coast Number = $1,375,000 / (1.07)²⁷ = $209,600

Marcus has $95K. His Coast Number is $210K. He is 45% there. The gap is $114,600. At $1,500/month in new contributions, he crosses the threshold in about 5 years — at age 43. Not at 30 like Sarah. But still 22 years before retirement. The math works. He just needs to keep going.

Linda, 45 — $280,000 invested

$50,000/year spending, plans to retire at 65, 7% real return

FIRE Number = $50,000 / 0.04 = $1,250,000

Coast Number = $1,250,000 / (1.07)²⁰ = $323,000

Linda has $280K. Her Coast Number is $323K. She is 87% there — the gap is $43,000. This is close. Two options: keep contributing $1,000/month and she crosses in about 3 years. Or cut spending from $50K to $45K, and her Coast Number drops to $290K. She has already passed it. The numbers move fast when you are this close.

All scenarios assume 4% SWR (Trinity Study), 7% real return, retirement at 65.

How This Calculator Works

The calculator runs one formula. Every number you see — your Coast FIRE threshold, the three growth projections, the chart — comes from this:

Real Return = Nominal Return − Inflation − Investment Fees

Default: 10% − 3% − 0% = 7% real return

That 7% is not a guess. It is the inflation-adjusted annual return of the S&P 500 from 1926 through 2025 — roughly 90 years of data including the Great Depression, stagflation in the 1970s, the 2008 financial crisis, and everything in between. Short-term returns swing wildly. Long-term returns do not.

The calculator shows three projection lines:

Scenario	Real Return	Assumes
Optimistic	8%	Above-average market conditions
Baseline	7%	Historical S&P 500 average (default)
Conservative	5%	Below-average or higher-fee portfolio

One variable people often overlook: investment fees. A 0.5% annual fee — common in actively managed funds — reduces your real return from 7% to 6.5%. Over 30 years of compounding, that 0.5% costs you roughly $150,000 on a $1.25 million target. The calculator lets you adjust this in Advanced Settings.

All calculations run in your browser. Nothing is sent to a server. The formulas are open source and verifiable on GitHub.

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Coast FIRE Calculator

Age Settings

Financial Settings

What Does Coast FIRE Mean?

What Is Your Coast FIRE Number?

Coast FIRE Number by Age

Three People, Three Numbers

Sarah, 28 — $62,000 invested

Marcus, 38 — $95,000 invested

Linda, 45 — $280,000 invested

How This Calculator Works

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