Coast FIRE / Financial Independence Calculator

Use our Coast FIRE Calculator to estimate your FIRE number, Coast FIRE number, and see whether your current investments could grow on their own to financial independence by retirement age.

Related Calculator: Advanced Real-World FIRE Calculator to Plan Early Retirement

What Is Coast FIRE?

Coast FIRE is a version of financial independence where you have already invested enough money that, if you stop adding new retirement contributions, your portfolio could still grow to your full FIRE target by retirement age.

That is the core idea.

You are not financially independent yet today. But you may have reached the point where your invested assets can “coast” on compound growth alone.

This is different from full FIRE.

With full FIRE, you already have enough invested now to cover your living expenses using a safe withdrawal rate.

With Coast FIRE, you still need to work and cover your current living expenses. But you may no longer need to keep aggressively saving for retirement because time and compounding could do the rest.

For beginners, the simplest way to think about it is this:

Coast FIRE means your retirement portfolio may already be on track, even if you stopped adding more money to it.

How to Use the Coast FIRE Calculator

This calculator works backward from your desired retirement lifestyle.

You enter:

• Your current age
• your retirement age
• Your current investment portfolio
• The annual spending you want in retirement
• Your safe withdrawal rate
• Your expected annual return
• inflation
• optional monthly contributions

The calculator first estimates your full FIRE number.

That is the amount you would need at retirement to support your target annual spending.

Then it discounts that number back to today using your expected real return. That gives your Coast FIRE number today.

The calculator also compares the required Coast FIRE number with your actual current portfolio and shows whether you are already there, close, or still behind.

Formula

The logic behind Coast FIRE is straightforward.

Step 1: Calculate your FIRE number

FIRE Number = Annual Spending ÷ Safe Withdrawal Rate

If you want to spend $50,000 per year and use a 4% withdrawal rate:

$50,000 ÷ 0.04 = $1,250,000

That means your full FIRE number is $1.25 million.

Step 2: Estimate real return

Because inflation matters, the calculator uses a real return estimate:

Real Return ≈ ((1 + Annual Return) ÷ (1 + Inflation)) − 1

This gives a more realistic growth rate in purchasing-power terms.

Step 3: Calculate the Coast FIRE number today

Coast FIRE Number Today = FIRE Number ÷ (1 + Real Return)^(Years to Retirement)

That is the amount you would need to invest today for it to grow to the full FIRE number by retirement.

Example Calculation

Suppose:

• Current age = 35
• Retirement age = 60
• Years to retirement = 25
• Desired annual spending = $50,000
• Withdrawal rate = 4%
• Expected annual return = 7%
• Inflation = 2.5%

Step 1: Full FIRE number

First, calculate the target portfolio needed at retirement:

$50,000 ÷ 0.04 = $1,250,000

So the full FIRE number is $1.25 million.

Step 2: Real return

Now estimate real return:

((1.07 ÷ 1.025) − 1) ≈ 4.39%

So the real return is about 4.39%.

Step 3: Coast FIRE number today

Now discount the FIRE number back over 25 years:

$1,250,000 ÷ (1.0439)^25 ≈ $427,000

So the Coast FIRE number today is roughly $427,000.

That means if you already had about $427,000 invested at age 35, and it compounded at that real rate, it could grow to about $1.25 million by age 60 without further retirement contributions.

Why Coast FIRE Matters

Coast FIRE matters because it can completely change how you think about work, saving, and financial freedom.

Once you reach Coast FIRE, your retirement may already be largely funded by time and compounding. That can open up more flexibility in the present.

For example, someone who reaches Coast FIRE may decide to:

• reduce work hours
• Take a lower-stress job
• switch careers
• Focus on family or lifestyle
• Stop aggressively maxing out retirement contributions

That does not mean they are fully retired. It means the long-term retirement math may be doing more of the heavy lifting from that point onward.

Coast FIRE vs Full FIRE

These concepts are related, but they are not the same.

Full FIRE means you already have enough invested now to support your target lifestyle.

Coast FIRE means you have enough invested now that, given enough time, it could grow into your full FIRE portfolio.

So:

• Full FIRE = financially independent today
• Coast FIRE = potentially financially independent by retirement without more retirement savings

That difference is important.

Coast FIRE is more about freedom of future retirement planning. Full FIRE is about immediate independence.

What Is a Good Coast FIRE Number?

A “good” Coast FIRE number is the number that realistically supports your target future spending.

That means it depends on:

• Your retirement spending target
• your withdrawal rate
• your years until retirement
• Your return assumptions
• Inflation

There is no single universal Coast FIRE number for everyone.

A younger person can usually reach Coast FIRE with a smaller current balance because they have more time for compounding. An older person usually needs a larger current balance because there is less time left.

Why Beginners Should Understand Coast FIRE

Coast FIRE is especially useful for beginners because it makes financial independence feel more reachable.

A lot of people assume FIRE means saving enormous amounts of money forever. Coast FIRE shows that there can be an important middle stage.

You do not necessarily need to reach full independence immediately. Reaching the point where your investments can grow on their own is already a major milestone.

That is encouraging because it shows how much value there is in:

• starting early
• staying consistent
• letting compounding do the work

Common Beginner Mistakes

One common mistake is assuming Coast FIRE means you can stop working completely. That is not usually what it means. You still need to support your current life until retirement.

Another mistake is using unrealistic return assumptions. A very optimistic return can make the Coast FIRE number look easier than it really is.

A third mistake is ignoring inflation. Inflation can materially reduce future purchasing power, so real return matters.

Beginners also sometimes underestimate how much changing the withdrawal rate affects the result. A lower withdrawal rate means a higher FIRE number, and therefore a higher Coast FIRE number today.

Why This Calculator Is Useful

This calculator is useful because it shows three important things at once:

• Your full FIRE number
• Your Coast FIRE number today
• How does your actual portfolio compare with that threshold

That turns Coast FIRE from an abstract idea into a clear planning milestone.

It can also help you answer practical questions such as:

• Am I already at Coast FIRE?
• How far away am I?
• How much more do I need to invest?
• What happens if I keep contributing?

FAQ