What Is Coast FI? How Coast Financial Independence Works

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Coast FI (coast financial independence, also called Coast FIRE) is the point at which your existing retirement investments, left to grow with no further contributions, are projected to reach the amount you need by your planned retirement age. After you reach it, your income only has to cover current living expenses. Retirement saving becomes optional.

Coast FI is not the same as being able to retire. You still have to work, or otherwise earn enough, until retirement. The difference is that the retirement portion of the plan is, on paper, already funded.

How to Calculate Your Coast FI Number

1. Estimate your retirement target. A common shortcut is to multiply expected annual retirement spending by 25, based on the 4% rule: historical U.S. stock and bond returns suggest a retiree could withdraw about 4% of the starting portfolio per year, adjusted for inflation, for roughly 30 years. Spending $40,000 a year implies a $1,000,000 target. The rule is a starting assumption, not a guarantee, and some planners use a lower withdrawal rate (a higher multiple) for longer retirements.

2. Count the years until retirement. Subtract your current age from your target retirement age. At 35 with a retirement age of 65, that is 30 years.

3. Choose a growth rate and discount the target. The formula is:

Coast FI Number = Retirement Goal ÷ (1 + r)^n

where r is the expected annual return and n is the years to retirement. This is the standard present-value formula: it asks how much money today grows into the target through compound interest.

Example of Coast FI

Hypothetical example. A 35-year-old wants $1,000,000 at 65 and assumes a 7% average annual return:

$1,000,000 ÷ (1.07)^30 = $1,000,000 ÷ 7.612 ≈ $131,367

If this person already has $150,000 invested for retirement, they have passed their Coast FI number. Under these assumptions they could stop contributing and the balance would still be projected to reach $1,000,000 by 65.

The assumptions matter as much as the arithmetic. Two variations on the same goal:

The second row shows the inflation problem. If the $1,000,000 target is stated in today’s dollars, the growth rate should be a real (after-inflation) return. Using a 7% nominal return against a goal in today’s dollars understates the number. The third row shows why the strategy depends on starting early: ten fewer years of compounding roughly doubles the amount needed now.

How Coast FI Is Used

Coast FI works as a checkpoint rather than an endpoint. People use it in a few ways:

• Changing work. Once retirement is funded on paper, some people move to a lower-paying but more satisfying job, cut hours, take a sabbatical or start a business.
• Partial coasting. Coast FI is not all or nothing. Many keep making smaller contributions as a safety margin while gaining flexibility.
• Continuing as before. If you like your work, reaching Coast FI simply means extra savings go toward retiring earlier, spending more later, helping family or leaving a larger estate.

The condition attached to all of these is that current income covers current expenses. Drawing down an emergency fund or the retirement account to cover a pay cut undoes the calculation, because the formula assumes the balance is left untouched.

Limitations of Coast FI

Several common errors make the projection look closer than it is:

• Optimistic returns. Markets do not deliver a steady average. A weak decade early on can leave the portfolio well short of its projected path.
• Ignoring inflation. Over 30 or 40 years, rising prices sharply reduce purchasing power. Use a real return, or inflate the target.
• Underestimating retirement spending. A paid-off mortgage may lower costs, but healthcare, travel and leisure often rise.
• Setting and forgetting. Children, divorce, job loss or a move can change both spending needs and the timeline.
• Starting late. Fewer years in the market shrink the compounding that makes coasting possible.
• Taxes and account type. A target based on pre-tax account balances may overstate spendable income if withdrawals are taxed.

Rechecking the numbers once a year, or after any major life event, keeps the projection honest. If the portfolio falls behind, resuming contributions closes the gap.

Coast FI vs. Related Terms

Coast FI vs. FIRE. Full financial independence under the FIRE movement means your portfolio can fund your living expenses now, so work becomes optional immediately. Coast FI covers only future retirement and still requires earned income until then.

Coast FI vs. Barista FI. Barista FI usually describes a portfolio that covers part of current expenses, with part-time work covering the rest. Coast FI draws nothing from the portfolio before retirement; work covers all current costs.

Coast FI number vs. FI number. The FI number is the full retirement target (for example, 25 times annual spending). The Coast FI number is that target discounted back to today, so it is always smaller as long as years remain and the assumed return is positive. It is also distinct from net worth: only invested assets earmarked for retirement count, not home equity or cash set aside for other goals.

The Bottom Line

Coast FI matters most to people who started saving early and want more freedom in how they work before retirement. It can support a lower-paying job, fewer hours or a career change, as long as current income covers current expenses and the retirement balance stays untouched. Use a realistic inflation-adjusted return and recheck the numbers yearly or after a major life event. If the portfolio falls behind, resume contributions.