Coasting to Retirement

Reaching financial independence does not always mean having enough money to stop working today. There is an earlier milestone—often called Coast FI or Coast FIRE—where the retirement savings you have already accumulated may be enough to grow into your retirement target over time.

If you have reached Coast FI, the calculation says you may no longer need additional retirement contributions to meet a particular retirement age and spending goal. Your existing investments are expected to do the remaining work through compound growth.

That does not necessarily mean you can retire now. You still need enough income to pay today’s expenses without drawing down the investments intended for retirement.

What does Coast FI mean?

“FI” stands for financial independence. “FIRE” commonly stands for financial independence, retire early.

Someone has reached Coast FI when:

Their current invested retirement assets are projected to grow to their modeled retirement target by their planned retirement age—even if they make no additional contributions.

The important words are projected, modeled, and planned. Coast FI is the result of a calculation built on assumptions. It is not an account designation, guaranteed outcome, or permanent status.

Your result depends on inputs such as:

• Current age
• Planned retirement age
• Current invested balance
• Expected retirement spending
• Social Security, pensions, or other retirement income
• Expected investment return
• Inflation
• Modeled withdrawal rate

Change any of these inputs and the Coast FI number changes.

What is the Coast FI number?

Your Coast FI number is the amount you would need invested today for that portfolio to grow to your retirement target without additional contributions.

A simplified calculation has two stages.

First, estimate the portfolio needed at retirement:

Retirement portfolio target = annual spending ÷ modeled withdrawal rate

Then discount that future target back to today:

Coast FI number = retirement portfolio target ÷ (1 + expected real return)years until retirement

The real return is the investment return remaining after accounting for inflation. Untap Wealth calculates it using:

Real return = (1 + nominal return) ÷ (1 + inflation) − 1

For example, a 7% expected return and 3% inflation produce a real return of approximately 3.88%, not exactly 4%.

The Untap Wealth calculator can also account for Social Security, pensions, and other income. Those sources reduce the amount the investment portfolio must provide, based on their timing and modeled value at retirement.

Compound growth is what makes coasting possible: growth in one period becomes part of the balance that can produce growth in later periods. Investor.gov provides a compound-interest calculator illustrating this relationship.

Coast FI is not full financial independence

Coast FI and full financial independence answer different questions.

Coast FI asks: If I leave my retirement investments alone, could they grow enough to fund my planned retirement?

Full FI asks: Do I have enough invested now to support my spending without relying on employment income?

A person who has reached Coast FI may still need a paycheck for housing, food, insurance, taxes, and other current expenses. The milestone only suggests that additional retirement contributions may no longer be mathematically necessary under the selected assumptions.

Example 1: Reaching Coast FI early in a career

Consider Maya, age 30.

She has:

• $425,000 invested
• A planned retirement age of 65
• Desired retirement spending of $60,000 per year in today’s dollars
• No Social Security, pension, or other income included in this simplified example
• A 4% modeled withdrawal rate
• A 7% expected nominal return
• A 3% inflation assumption

Her estimated retirement portfolio target is:

$60,000 ÷ 4% = $1,500,000

After inflation, the assumed real return is approximately 3.88%. With 35 years until retirement, her Coast FI number is approximately:

$1,500,000 ÷ 1.038835³⁵ = $395,332

Maya’s $425,000 portfolio is about $29,700 above the modeled Coast FI number. If the assumptions hold and she makes no further contributions, the model projects approximately $1.61 million in today’s dollars at age 65.

Maya has not reached full financial independence. She still needs income for her current lifestyle. But the calculation gives her options.

She might choose to:

• Continue contributing and pursue an earlier retirement date
• Build a larger margin for uncertainty
• Reduce contributions and direct money toward other goals
• Move to a lower-paying but more satisfying career
• Work fewer hours
• Take a career break
• Accept more uncertainty in current income

Years of aggressive early saving have given compound growth more time to work. That time is a major part of Maya’s financial flexibility.

Example 2: Reaching Coast FI ten years before retirement

Now consider Daniel, age 55.

He has:

• $1,100,000 invested
• A planned retirement age of 65
• The same $60,000 retirement spending goal
• No outside retirement income included
• The same 4% modeled withdrawal rate
• A 7% nominal return
• A 3% inflation assumption

Daniel also has a $1.5 million retirement target. But he has only 10 years for his investments to grow.

His Coast FI number is approximately:

$1,500,000 ÷ 1.038835¹⁰ = $1,024,768

Daniel’s $1.1 million portfolio is about $75,200 above the modeled Coast FI number. With no additional contributions, it is projected to reach approximately $1.61 million in today’s dollars at age 65.

Daniel has reached Coast FI under these assumptions, but his shorter timeline makes the result more sensitive to near-term performance. He has much less time than Maya to recover from a downturn or compensate for underperformance.

Coasting could still give Daniel useful flexibility. He might reduce overtime, move to a less demanding role, or direct some income toward near-term needs. But the calculation offers less room for error than it initially appears.

The mathematical risks of coasting

Expected return is not a forecast

A Coast FI calculation usually applies one steady return across many years. Actual investment returns vary, and the compound—or geometric—return that an investor ultimately receives may be lower than the assumed rate.

The assumed return has a large effect on the result:

InvestorCoast number at 2% real returnAt 3.88% real returnAt 5% real return

Maya, age 30

About $750,000

About $395,000

About $272,000

Daniel, age 55

About $1.23 million

About $1.02 million

About $921,000

A result based on an optimistic return can make someone appear Coast FI much sooner than a more conservative scenario would.

A market downturn can erase a narrow margin

Suppose both investors experience an immediate 25% decline.

Maya’s $425,000 becomes $318,750. Under the original assumptions, it would grow to approximately $1.21 million, leaving a projected shortfall of roughly $291,000. The model estimates that restoring the original target would require contributions of approximately $337 per month for the remaining 35 years.

Daniel’s $1.1 million becomes $825,000. That balance would also grow to approximately $1.21 million, but he has only 10 years remaining. Closing the gap would require approximately $2,041 per month under the same model.

The proportional loss is identical, but the recovery burden is very different. Time gives the younger investor more opportunities to recover or resume contributions.

Stocks remain risky even over long periods, and a decline near a planned retirement date can require the investor to change that plan. FINRA illustrates this long-term market risk.

Sequence of returns requires careful wording

If a portfolio receives no deposits or withdrawals, rearranging the same series of annual returns does not change the ending balance. Multiplication gives the same result regardless of order.

For example:

$100 × 1.20 × 0.80 = $96

and:

$100 × 0.80 × 1.20 = $96

During a pure coast period, the order alone is not the issue. The important risk is whether the realized compound return—and therefore the ending balance—matches the model by the required date.

Order becomes especially important when money is entering or leaving the portfolio. Once retirement withdrawals begin, an early downturn can force an investor to sell more investments at reduced prices, leaving fewer assets available for a later recovery. Vanguard identifies downturns just before or during retirement as particularly consequential when withdrawals are involved. Vanguard retirement-risk guidance.

A Coast FI number without a buffer is a break-even estimate

If your portfolio only barely exceeds the calculated Coast FI number, the model has little room for:

• Lower investment returns
• Higher inflation
• Investment fees
• A longer retirement
• Higher retirement spending
• A lower withdrawal rate
• A later reduction in expected Social Security or pension income
• Moving the retirement date earlier
• Withdrawals from the portfolio before retirement

Reaching the number exactly means reaching the modeled threshold—not eliminating uncertainty.

What can change after reaching Coast FI?

Coast FI can create choices rather than dictate one decision.

Someone who saved aggressively early may decide to take their foot off the gas. That could mean reducing contributions instead of stopping them, continuing only enough to receive an employer match, or redirecting cash flow toward other priorities.

It may also expand career options. When future retirement contributions are no longer a strict mathematical requirement, a person may have more room to choose work based on schedule, purpose, location, stress, or flexibility—not salary alone.

Continuing to contribute remains valuable. Additional investments may:

• Create a buffer against underperformance
• Support a higher retirement lifestyle
• Make an earlier retirement possible
• Offset changes in inflation or expected returns
• Reduce dependence on a precise withdrawal assumption

Coast FI should therefore be viewed as a new range of choices, not an instruction to stop saving.

How to use a Coast FI calculation responsibly

A single result is only a starting point. Consider testing several scenarios:

1. Lower the expected return.
2. Increase inflation.
3. Use a lower modeled withdrawal rate.
4. Reduce expected outside income.
5. Increase retirement spending.
6. Model a major market decline.
7. Compare stopping contributions with continuing a smaller amount.
8. Recalculate periodically as balances, goals, and assumptions change.

Diversification can help manage investment risk, although it cannot guarantee against losses. Investor.gov also emphasizes matching asset allocation to time horizon and adjusting risk as retirement approaches. Investor.gov saving and investing guidance

Coast FI is a planning milestone, not a promise. Its real value is showing how time, accumulated savings, and future assumptions interact—and what choices may become available when you have already done much of the saving.

Explore your own Coast FI scenario

Use the Coast FI calculator to estimate your Coast FI number, test different retirement ages and spending levels, and see how changes in return, inflation, future income, and contributions affect the result.

All examples are hypothetical, rounded, stated in today’s dollars, and exclude taxes, fees, and outside retirement income unless noted. They do not represent any particular investment or guaranteed outcome. This educational content is general information, not individualized financial, investment, tax, or legal advice.