Coast FIRE Explained: How to Find Your Coast Number

Coast FIRE is a projection before full financial independence. For an illustrative 32-year-old targeting $1 million at 65, about $200,000 could grow to the target at a constant 5% return after inflation and fees, with no further contributions or withdrawals. The calculation does not establish that future returns or spending will follow the plan.

What is Coast FIRE in plain language?

Coast FIRE means existing investments are projected to reach a future retirement target without more contributions under chosen assumptions. Current expenses still need another funding source. Before reducing saving, test lower returns, higher spending, and a different retirement date, and decide when contributions would resume.

That single change quietly rewrites your relationship with work. A job that must fund your current life is a much smaller ask than one that must fund your current life plus a seven-figure goal. Need a concrete test? If you could drop your retirement contributions to zero tomorrow and still hit your number on schedule, you have coasted.

How is Coast FIRE different from full FIRE?

Full FIRE requires a portfolio that can pay for your life immediately, typically about 25 times annual spending under the 4% rule. Coast FIRE only requires the seed of that portfolio, planted early enough to grow. Same destination, very different arrival dates.

Milestone	What it means	Potential flexibility if the plan holds
Coast FIRE	Assumed growth reaches a future target	Reduced retirement contributions
Barista FIRE	Part-time income plus planned withdrawals cover spending	Full-time work
Full FIRE	Withdrawals are planned to cover spending	All work

The order matters. Everyone on a FIRE path passes through Coast FIRE first, usually years before full independence, whether they notice the crossing or not. Noticing is the useful part.

The Coast FIRE formula: why time does the heavy lifting

Compounding is exponential, so the years furthest from your target date are the most valuable ones. At a 5% real (after-inflation) return, money roughly doubles every 14 years, a pace you can verify with the SEC's compound interest calculator . A dollar invested at 32 doubles twice by 60-something; a dollar invested at 55 doubles once, if that. This is why the coast number depends so heavily on how far away the target date is:

Years until target	Needed today to coast to $1,000,000 (5% real)
10 years	~$614,000
15 years	~$481,000
20 years	~$377,000
25 years	~$295,000
33 years	~$200,000

The formula behind the table is one line: divide the FIRE number by (1 + real return) raised to the years remaining. Using real returns keeps everything in today's dollars, so you can compare the coast number directly against your current portfolio balance.

What does Coast FIRE look like with real numbers?

Take the worked example we use across this series. Maya is 32, spends $40,000 a year, has $100,000 invested, and adds $12,000 a year. Her FIRE number at a 4% withdrawal rate is $1,000,000, and at a 5% real return her contributions carry her there in about 27 years.

Her projected Coast FIRE number at 32 is $1,000,000 ÷ 1.05³³, about $200,000. With $100,000 initially invested and $12,000 added at each year-end, she reaches about $342,000 at age 43 under the same constant 5% real-return assumption. That is close to the target discounted over the remaining 22 years. Stopping contributions would leave the result dependent on those returns and an unchanged spending goal, so it calls for periodic review.

You can reproduce every number in this example with the FIRE number calculator. Enter your annual spending, current portfolio, yearly contribution, and a real return assumption; it returns your FIRE number, your estimated independence year, and the coast amount for that same timeline.

What does reaching Coast FIRE actually buy you?

If the projection remains adequate, reducing retirement contributions can free some current income for other needs. That flexibility depends on the plan continuing to work; it is not a permanent exemption from saving.

• Flexibility in spending. A saver putting away $12,000 a year who coasts can absorb a $12,000 hit to income or expenses without touching the plan.
• Lower pressure. Market dips feel different when you need growth eventually rather than contributions now. So do layoffs.
• Career choice. Work that pays less but means more becomes affordable. The portfolio no longer cares which job covers your groceries.

What are the limits and risks of coasting?

A coast plan leans on market growth for decades, and decades are long enough for assumptions to break. Treat these four honestly before you stop contributing:

• Investment risk. A 5% real return is an assumption, not a promise. A long stretch of weak markets can leave the portfolio short with little time to recover, which is why conservative assumptions beat optimistic ones here.
• Spending changes. The FIRE number is built from today's spending. Kids, housing, or lifestyle growth raise the target, and a raised target un-coasts you retroactively.
• Taxes. Withdrawals from pre-tax accounts are taxable income. If your spending figure ignores that, your real target is higher than the one you coasted to.
• Healthcare. Anyone stepping back from full-time work before traditional retirement age needs a plan for insurance, and it is rarely cheap.

The practical defense is monitoring, not pessimism. Coast FIRE is a threshold you hold, not a box you tick once, so check your real balances against the coast line at least yearly. A net worth view that updates from your actual accounts makes that a glance instead of a spreadsheet session, and portfolio tracking keeps the "invested today" input honest.

Check your Coast FIRE amount

You may be closer to this milestone than you think, especially if you started investing in your twenties. Open the FIRE number calculator, enter your real numbers, and compare the coast amount it reports against your current portfolio. Then keep reading the series: how the 4% rule sets the target this whole calculation aims at, and where passive income fits once the portfolio starts doing the earning. New to the framework? Start with our beginner's guide to FIRE .

Educational content, not personal financial advice. Projections assume constant returns and cannot guarantee any outcome.

The Investor.gov compound-interest calculator lets you vary time, rates, and contributions. For a coast scenario, set new contributions to zero, use a return after inflation and fees when the target is in today's dollars, and account for withdrawal taxes in the spending target.