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Coast FIRE Explained: Calculate Your Coast Number

Coast FIRE offers a different way to think about retirement savings. Instead of asking when you can stop working altogether, you ask whether the money you have already invested could grow enough to support retirement later—even if you make no further retirement contributions.

The answer depends on your timeline, spending needs, and investment assumptions. We’ll walk through a straightforward calculation and show you how to test it before making changes to your savings plan.

What Coast FIRE Means

FIRE stands for financial independence, retire early. At full financial independence, your investments and other resources are expected to cover your living expenses. Coast FIRE is an earlier milestone: your existing retirement investments are projected to grow to your retirement target by the time you need them.

You generally still need income to pay for housing, food, insurance, and other current expenses. The potential difference is that you may have more flexibility to reduce retirement contributions and direct that money toward other priorities.

For example, someone who reaches their projected coast number might consider a less demanding job or save for a different goal. But reaching that number is not a guarantee of retirement security. Markets fluctuate, costs change, and a projection cannot predict what will happen over several decades.

Calculate Your Coast FIRE Number

Your coast number is the amount you would need invested today, under a set of assumptions, to reach your retirement savings target without additional contributions.

1. Set a retirement target

Start by estimating your annual retirement spending. Consider housing, food, travel, healthcare, taxes, and any other expenses you expect. Then estimate how much of that spending your investments will need to cover after accounting for income sources such as Social Security.

One way to frame a target is to divide the amount your portfolio must cover each year by an assumed withdrawal rate. For example, $40,000 divided by 4% produces a $1 million target. A withdrawal rate is a planning assumption, not a guarantee that your money will last.

2. Choose a timeline and return

Count the years from now until you expect to begin using your retirement savings. Then select an assumed annual investment return. If your target is expressed in today’s dollars, use an inflation-adjusted return. If your target includes future inflation, use a nominal return instead.

The Investor.gov compound interest calculator can help you explore how a balance might grow under different assumptions.

3. Apply the formula

Coast number = retirement target ÷ (1 + annual return)years until retirement

Enter the annual return as a decimal: 5% becomes 0.05. The example below uses an inflation-adjusted return and a target stated in today’s dollars.

Illustrative Coast FIRE Calculation

Input	Example
Retirement savings target	$1,000,000
Years until retirement	25
Assumed annual return after inflation	5%
Estimated coast number	About $295,300

In this simplified example, roughly $295,300 invested today would grow to $1 million in 25 years at a steady 5% annual return after inflation. Compare the result with your current invested retirement savings. Leave out assets you do not intend to use for retirement, such as a separate emergency fund.

Test the Assumptions Before You Coast

A single estimate is a starting point, not a finish line. Keeping the $1 million target and 25-year timeline, a 3% inflation-adjusted return raises the required starting balance to about $477,600. At 5% over only 20 years, the estimate rises to about $376,900. A higher spending target also increases the amount you need today.

Run a range of scenarios before deciding whether to reduce contributions. Consider investment fees, taxes, healthcare costs, and changes in your household or expected retirement date. Make sure your return and spending assumptions reflect the costs relevant to your plan rather than counting the same cost twice.

Keep an emergency fund separate from your retirement investments, and revisit your calculation periodically. Real returns will not arrive at a steady rate, and investment losses are possible. For a primer on risk and saving, see Investor.gov’s saving and investing resources.

Use the Guide to Explore Your Own Plan

Our Coast FIRE Explained: Your Ultimate Guide to Understanding and Calculating Coast FIRE is a resource for exploring the concept and its calculations. It is listed at $11.99 USD. As you learn, consider which retirement date, savings balance, and spending assumptions fit your circumstances—and which deserve another look.

Tracking everyday spending can also help you build a more realistic estimate of what you may need. If you are organizing your finances alongside that exercise, our Calvin Klein Jeans Women’s Grey Print Wallet with Zip Fastening is another option in our store. A wallet won’t replace a budget, but keeping payment cards organized can support your day-to-day routine.

Our team recommends treating your coast number as a planning checkpoint rather than permission to stop paying attention. You can adjust your contributions as your circumstances change, and a qualified financial professional can help you assess decisions involving taxes, investments, and retirement income.

FAQ

Does Coast FIRE mean you can stop working?

Not necessarily. Coast FIRE generally assumes you still have income to cover current living expenses while your invested retirement savings grow.

What return should I use to calculate my coast number?

Use a considered assumption and test several scenarios, since actual returns vary. Pair an inflation-adjusted return with a retirement target expressed in today’s dollars.