What Is Coast FIRE? The Halfway Point to Financial Independence

Coast FIRE is a milestone on the path to financial independence where your current investments will grow to your full retirement target by themselves — without any further contributions. Once you reach your Coast FIRE number, you only need to earn enough to cover your living expenses until retirement. You can stop saving aggressively, take a lower-paying job, work part-time, or simply relax — your money does the heavy lifting from here.

The Core Idea

The FIRE movement's standard goal is accumulating 25× your annual expenses (the 4% rule). If you spend $50,000/year, your full FIRE number is $1,250,000.

Coast FIRE asks a different question: how much do you need invested right now so that compound growth gets you to $1,250,000 by a target retirement age — without adding another dollar?

The answer is your Coast FIRE number, and it is always smaller than your full FIRE number. How much smaller depends on how many years you have until retirement and your expected investment return.

The Formula

Coast Number = FIRE Number ÷ (1 + r)^n

Where:

• FIRE Number = Annual expenses ÷ withdrawal rate (usually 4%)
• r = Expected annual return (e.g. 0.07 for 7%)
• n = Years until retirement (retirement age − current age)

Example: $50k/year expenses, 7% return, retire at 65, currently 30 years old.

Step	Calculation	Result
FIRE number	$50,000 ÷ 4%	$1,250,000
Years to retirement	65 − 30	35 years
Discount factor	(1.07)^35	10.68×
Coast number	$1,250,000 ÷ 10.68	≈ $117,000

With $117,000 invested at age 30 and a 7% annual return, that money grows to $1.25M by age 65 without a single additional contribution.

Use the Coast FIRE Calculator to find your own number instantly.

Why Coast FIRE Is a Game-Changer

Most savings advice focuses on how much to save each month. Coast FIRE reframes the question: once you hit a certain threshold, the math takes over. This is powerful because:

1. You can downshift earlier. Instead of grinding toward $1.25M, you grind toward $117k (at 30). That could take 3–5 years instead of 20+.
2. Reduces financial anxiety. Knowing retirement is "handled" even if you never save another dollar creates enormous peace of mind.
3. Enables career flexibility. Coast FIRErs often take lower-stress, lower-pay jobs because the retirement savings pressure is gone. "Barista FIRE" is a popular variant — working part-time for health insurance and living expenses while investments coast.

Coast FIRE vs Other FIRE Variants

Variant	What it means
Traditional FIRE	Portfolio is large enough to retire now (live off withdrawals immediately)
Coast FIRE	Portfolio will reach retirement size by target retirement age — still working for expenses
Barista FIRE	Coast + part-time work for health benefits and daily expenses
Lean FIRE	Retire now but on a very frugal budget (often < $40k/year)
Fat FIRE	Retire now with a comfortable/generous budget (often $80–100k+/year)

What Return Rate to Use

Long-run US stock market returns:

• Nominal (before inflation): ~10% historically
• Real (after ~3% inflation): ~7%

Using 7% real is standard for Coast FIRE calculations because your expenses in retirement will also be in future (inflated) dollars. The two effects roughly cancel. If your portfolio is concentrated in bonds or more conservative assets, use 4–5%.

Common Mistakes

Using too high a return rate. 10% nominal sounds conservative but after inflation that's only 7% real. For a 35-year horizon, the difference between 7% and 10% is massive.

Forgetting expenses change. Today's $50,000 lifestyle may cost $80,000 in 30 years. Account for this by either using a real return rate (which handles inflation on both sides) or inflating your expense estimate explicitly.

Treating Coast as full retirement. You still need income until retirement. Coast FIRE only solves the investment side — not the "how do I pay rent next month" side.

Is Coast FIRE Right for You?

Coast FIRE is most compelling for:

• People in their late 20s or early 30s who have a meaningful savings head-start
• Anyone burned out on aggressive saving and willing to trade some retirement acceleration for current quality of life
• People in high-cost careers who want permission to switch to something lower-paid but more fulfilling

If you're later in your career (50+), the discount factor shrinks and Coast FIRE is less impactful — the gap between your Coast number and your full FIRE number narrows.

Use the Coast FIRE Calculator to find your number, then compare with the FIRE Number Calculator to see how close you are to full FIRE.