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DDonnie · Your AI financial expertupdated Nov 12, 2026

Coast FIRE calculator: can you stop saving for retirement yet?

Key takeaways
  • A Coast FIRE calculator tells you how much you need invested today to stop saving for retirement: that's your Coast FIRE number. That money then grows on its own until you retire. FIRE stands for Financial Independence, Retire Early.
  • The calculation: subtract your Social Security from your monthly spending in retirement, then multiply by 12 and by 25. Finally, divide by what $1 invested today becomes by the time you retire. The × 25 comes from the 4% rule, tested on retirements of 15 to 30 years [1]. For a longer retirement, keep a margin: at 3% a year, it's about × 33.
  • Example: you're 35 and have $100,000 invested at 5% a year after inflation. You want to spend $4,000 a month starting at 67, with $2,000 of it paid by your public pension (Social Security). You need $600,000 at 67, and your Coast FIRE number is about $126,000: you're about $26,000 short today.
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The Coast FIRE calculation, using the tool's example
StepExample
AssumptionsAge 35, $100,000 invested, retirement at 67, 5% a year after inflation
Your spending in retirement, minus your Social Security$4,000 − $2,000 = $2,000 a month
What your savings must pay each year$2,000 × 12 = $24,000
What you need at 67 (× 25, the 4% rule)$24,000 × 25 = $600,000
What $1 invested becomes in 32 years at 5% a yearabout $4.76
Your Coast FIRE number$600,000 ÷ 4.76 ≈ $126,000
With your $100,000 investedyou're about $26,000 short today
1

What is Coast FIRE?

Coast FIRE is the point a Coast FIRE calculator looks for: the savings you already have invested are enough for your retirement, without adding a single dollar. You still work, but only to pay for your monthly spending.

Coast FIRE is a stage of FIRE, the early retirement movement. To stop working early, the full calculation is in our guide to retiring early.

  • FIRE stands for Financial Independence, Retire Early.
  • Coast means your money coasts: it grows on its own until you retire.
  • Example: at 35, you have $130,000 invested at 5% a year. At 67, it grows to about $619,000 without adding anything. If your goal is $600,000, you're Coast FIRE.
  • What Coast FIRE changes: a part-time job or a lower-paying job becomes possible, because you no longer need to save for retirement.
2

How to calculate your Coast FIRE number in 4 steps

Your Coast FIRE number is the amount you need invested today to reach your retirement goal without adding anything. The Coast FIRE calculator does these 4 steps for you.

The example's assumptions: you're 35 and plan to retire at 67. You want to spend $4,000 a month, Social Security pays $2,000 of it, and your money earns 5% a year after inflation.

  1. Subtract your Social Security from your spendingYou want to spend $4,000 a month and Social Security pays $2,000 of it. Your savings must pay $2,000 a month, or $24,000 a year.
  2. Multiply by 25$24,000 × 25 = $600,000. That's what you need at 67 to withdraw 4% a year, because 4% of $600,000 is $24,000.
  3. Calculate what your money becomes by retirementFrom 35 to 67, you have 32 years left. At 5% a year, each dollar invested today becomes about $4.76 at 67.
  4. Divide, then compare$600,000 ÷ 4.76 ≈ $126,000: that's your Coast FIRE number. With $100,000 invested, you're about $26,000 short today.
The word to know
Compound interest : The gains on your money earn gains of their own. Example: $100,000 at 5% a year becomes $105,000 after one year, then $110,250 after two years, because the $5,000 gain earns too.
3

The × 25: the 4% rule and its limits

The × 25 comes from the 4% rule: each year of retirement, you withdraw the same amount, equal to 4% of your savings on the day you retire. Withdrawing 4% a year means having 25 times what you withdraw, because 100 ÷ 4 = 25.

The rule is based on a study published in 1998 in the AAII Journal [1]. The AAII is the American Association of Individual Investors. The study's conditions:

  • US markets from 1926 to 1995 [1].
  • Retirements of 15, 20, 25 and 30 years [1].
  • Portfolios ranging from 100% stocks to 100% bonds [1].
  • Its conclusion: with a portfolio mostly in stocks, withdrawing 3% or 4% a year is a very cautious choice [1].

In the example, you retire at 67: a 30-year retirement takes you to 97, within the study's conditions.

Watch outThe study did not test retirements longer than 30 years [1]. If you retire at 55 and plan for your money to last until 95, your retirement lasts 40 years. Keep a margin, for example by withdrawing 3% a year: 100 ÷ 3 ≈ 33.3, so $24,000 × 33.3 ≈ $800,000 instead of $600,000.
4

Coast FIRE and retirement: your Social Security and your retirement age

Your public pension, Social Security, lowers your Coast FIRE number a lot. Your savings only pay what Social Security doesn't cover.

  • Without Social Security: your savings pay $4,000 a month. You need $48,000 × 25 = $1,200,000 at 67, and your Coast FIRE number doubles, to about $252,000.
  • With $2,000 of Social Security: you need $600,000 at 67, and your number is about $126,000.
  • Full retirement age: if you were born on January 2, 1960 or later, you get your full benefit at 67 [2].
  • Retiring earlier: you can claim Social Security from age 62, but the longer you wait, the higher it is [3]. At 62, or 60 months before 67, your benefit drops by 30% [4]: 36 months × 5/9% = 20%, then 24 months × 5/12% = 10%.
  • Example, retiring at 62: your benefit goes from $2,000 to $1,400 a month. Your savings pay $2,600 a month, so you need $780,000 at 62 ($2,600 × 12 × 25).
  • Your number goes up: from 35 to 62, you have 27 years left, and $1 invested at 5% a year becomes about $3.73. Your Coast FIRE number rises to about $209,000 ($780,000 ÷ 3.73).

Estimate your benefit on the Social Security website, then enter that amount in the tool.

5

Coast FIRE: the return changes everything

The return you assume can nearly triple your Coast FIRE number. The table keeps the example: $100,000 invested at 35 and $600,000 needed at 67, or 32 years. Your number then ranges from about $93,000 at 6% a year to $272,000 at 2.5%.

This is a simulation, not a promise.

Return per yearYour $100,000 at 67Your Coast FIRE number2.5% (cautious assumption)about $220,000about $272,0004% (middle assumption)about $351,000about $171,0005% (tool's default)about $476,000about $126,0006% (optimistic assumption)about $645,000about $93,000
  • At 2.5% a year, your $100,000 falls well short: you're about $172,000 short today.
  • At 6% a year, your $100,000 already beats your number by about $7,000.
  • Use a return after inflation: in the example, the $4,000 a month is in today's dollars, without price increases.
The word to know
Return after inflation : What your money earns once price increases are taken out. Example: your money earns 7% a year and prices rise 2%: you earn about 5% after inflation.
Watch outA return that's too optimistic throws off your calculation. Example: going from 5% to 6% lowers your number from about $126,000 to $93,000. If markets do worse, your money won't reach $600,000 at 67.
6

Not Coast FIRE yet? 3 ways to close the gap

Three levers close the gap: contribute for a few years then stop, lower your planned spending, or invest a lump sum. In the example, you're about $26,000 short today, or about $123,500 at 67 ($600,000 − $476,500).

  • Contribute for a few years, then stop: $6,000 a year ($500 a month) from 35 to 40. At 40, you have about $160,800: $127,600 from your $100,000 (× 1.276) and $33,200 from your 5 contributions ($6,000 × 5.53). Your Coast FIRE number at 40 is about $160,700 ($600,000 ÷ 3.73): you can stop saving.
  • Lower your planned spending: with $3,500 a month instead of $4,000, your savings pay $1,500 a month. You need $450,000 at 67, for a number of about $94,000: your $100,000 is already enough.
  • Invest a lump sum: about $26,000 today, for example a bonus, and you reach your Coast FIRE number.
7

Coast FIRE calculator for a couple

For a couple, add everything up: your combined planned spending, both your Social Security benefits and all the money you have invested. The Coast FIRE calculation stays the same.

  • Example: you're both 35 and plan to retire at 67. You want to spend $6,000 a month together, and your Social Security benefits pay $2,000 + $1,500 = $3,500.
  • What you need: $6,000 − $3,500 = $2,500 a month, and $2,500 × 12 × 25 = $750,000 at 67.
  • Your Coast FIRE number: $750,000 ÷ 4.76 ≈ $157,000. With $90,000 + $60,000 = $150,000 invested, you're about $7,000 short.
  • If your ages differ: run the calculation for each of you, with each person's share of spending, Social Security, money invested and retirement age. Then add the two numbers together.
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Your questions

What is the best Coast FIRE calculator?

The best Coast FIRE calculator shows you its assumptions and lets you change them: age, money invested, spending, Social Security, retirement age and return. The tool on this page shows all 6, with 5% a year by default.

What does a Coast FIRE calculator do?

A Coast FIRE calculator does the 4 steps of the calculation at once, and redoes them as soon as you change a number. Example: raise your planned spending from $4,000 to $4,500 a month, and your number goes up from about $126,000 to $157,000.

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Sources

  1. Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable · AAII Journal (Carl M. Hubbard) · February 1998
  2. 20 CFR 404.409, What is full retirement age? · U.S. Government Publishing Office (govinfo), Code of Federal Regulations · April 1, 2025 edition
  3. Retirement · USAGov · July 30, 2026
  4. 20 CFR 404.410, How does SSA reduce my benefits when my entitlement begins before full retirement age? · U.S. Government Publishing Office (govinfo), Code of Federal Regulations · April 1, 2025 edition

This article is for education only. It is not investment advice: investing carries a risk of loss.

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