Your Coast FIRE Number Depends on One Thing: Time
The single biggest factor in your Coast FIRE number isn't your income, your savings rate, or the market — it's how many years you have until retirement. More years means more time for compound growth, which means a lower Coast FIRE target.
A 25-year-old needs far less invested today than a 45-year-old because they have 15 extra years of compounding. That's not just a little difference — it can be $200,000+ less.
Below, we break down the exact Coast FIRE numbers by age, using multiple spending levels and market assumptions. All numbers use the standard 4% rule and are adjusted for inflation (real returns).
Assumptions Used
- Retirement age: 65
- Return scenarios: Conservative (5% return / 4% inflation = 1% real), Moderate (7% / 3% = 3.88% real), Aggressive (10% / 2% = 7.84% real)
- 4% withdrawal rule (25x annual expenses)
- All numbers in today's dollars
Coast FIRE Numbers by Age
If You Plan to Spend $40,000/Year in Retirement
| Age | Conservative | Moderate | Aggressive |
|---|---|---|---|
| 25 | $670,000 | $222,000 | $55,000 |
| 30 | $705,000 | $270,000 | $79,000 |
| 35 | $741,000 | $329,000 | $114,000 |
| 40 | $779,000 | $401,000 | $164,000 |
| 45 | $819,000 | $489,000 | $237,000 |
If You Plan to Spend $60,000/Year in Retirement
| Age | Conservative | Moderate | Aggressive |
|---|---|---|---|
| 25 | $1,005,000 | $333,000 | $82,000 |
| 30 | $1,057,000 | $406,000 | $119,000 |
| 35 | $1,112,000 | $494,000 | $171,000 |
| 40 | $1,169,000 | $602,000 | $247,000 |
| 45 | $1,228,000 | $733,000 | $355,000 |
If You Plan to Spend $80,000/Year in Retirement
| Age | Conservative | Moderate | Aggressive |
|---|---|---|---|
| 25 | $1,340,000 | $444,000 | $109,000 |
| 30 | $1,410,000 | $541,000 | $158,000 |
| 35 | $1,482,000 | $659,000 | $228,000 |
| 40 | $1,558,000 | $803,000 | $329,000 |
| 45 | $1,638,000 | $978,000 | $474,000 |
Want your exact number with custom inputs? Use our Coast FIRE Calculator.
What These Numbers Actually Mean
At age 25 with moderate assumptions, you need about $222,000 invested to never save for retirement again (at $40K/year spending). That's achievable for someone who starts saving $1,500/month at 22 and gets market returns.
At age 35, that number jumps to $329,000. You've lost 10 years of compounding, so you need more capital to start with.
At age 45, it's $489,000. Still very achievable — but the window for "coasting" is narrower.
The lesson is clear: every year you delay costs you. Not because saving is harder, but because you lose compounding time.
Coast FIRE by Age: Detailed Breakdown
Age 25: The Ultimate Head Start
Coast FIRE Number (Moderate): ~$222,000 for $40K/year retirement
At 25, you have the most powerful asset in finance: 40 years of compounding. Even with conservative assumptions, $222,000 invested in a total market index fund has an overwhelming probability of reaching $1M+ by 65.
How to get there:
- Save $1,500/month for 10 years starting at age 22 = ~$250,000 (with returns)
- Or save $2,500/month for 6 years starting at 25
The opportunity: If you hit Coast FIRE at 25, you have 40 years of career flexibility. You could become a teacher, travel the world, start a nonprofit — anything that covers daily expenses.
Age 30: The Sweet Spot
Coast FIRE Number (Moderate): ~$270,000 for $40K/year retirement
Age 30 is where most people in the FIRE community start getting serious. You likely have some career earnings behind you, and you still have 35 years of compounding ahead.
How to get there:
- If you've been saving since 25 in a 401(k), you might already be close
- $270,000 equals roughly 5 years of maxing out a 401(k) + IRA with employer match and market returns
Real example: Sarah, a software engineer, saved 40% of her $90,000 salary from age 24-30. With employer match and market returns, she hit $285,000 at 30. She's Coast FIRE. She now works as a UX designer at a nonprofit for $55,000 and hasn't touched her retirement accounts.
Age 35: The Decision Point
Coast FIRE Number (Moderate): ~$329,000 for $40K/year retirement
At 35, many people are facing big life decisions: marriage, kids, career pivots. This is often when the question "Can I afford to downshift?" becomes urgent.
How to get there:
- $329,000 is roughly $27,000/year invested for 10 years (with 7% returns)
- That's $2,250/month — aggressive but doable on a median household income
The calculation that changes everything: If you're 35 with $200,000 invested, you're already 61% to Coast FIRE. Use the reverse calculator to find out exactly how much more you need per month.
Age 40: It's Not Too Late
Coast FIRE Number (Moderate): ~$401,000 for $40K/year retirement
At 40, you have 25 years until traditional retirement. The Coast FIRE number is higher, but so is your likely income. Many 40-year-olds are at their peak earning years.
How to get there:
- If you have $250,000 invested, you need roughly $150,000 more
- That's $1,800/month for 5 years with market returns
- Or consider using the Barista FIRE simulator — part-time income in retirement dramatically lowers the target
Age 45: Sprint or Adjust
Coast FIRE Number (Moderate): ~$489,000 for $40K/year retirement
At 45, the math gets tighter. With only 20 years of compounding, your money has less time to grow. But don't be discouraged — $489,000 is very achievable, especially if you've been saving at all throughout your career.
Strategies at 45:
- Reduce planned retirement spending to lower the target
- Consider Barista FIRE (part-time income reduces the target by 30-50%)
- Delay retirement to 67 — even 2 extra years drops the number significantly
- Use aggressive allocation if your risk tolerance allows
The Power of Starting Early: A Visual Comparison
Consider two people who both invest $500/month:
Person A starts at 22:
- By age 30: $62,000
- By age 35: $106,000
- By age 40: $170,000
- Coast FIRE at ~28
Person B starts at 32:
- By age 40: $62,000
- By age 45: $106,000
- Coast FIRE at ~43
Same monthly contribution. But Person A reaches Coast FIRE 15 years earlier because they started 10 years sooner. That's the math of compounding.
What to Do After You Hit Your Number
Reaching Coast FIRE doesn't mean you stop working. It means you stop working for retirement. Here's what changes:
-
Career choices become about fulfillment, not salary. You can optimize for meaning, not money.
-
Savings pressure vanishes. You only need to earn enough for today's expenses. No more maxing out 401(k) contributions.
-
Risk tolerance changes. Want to start a business? The downside is smaller because your retirement is already funded.
-
Mental health improves. Financial anxiety is one of the top stressors in America. Removing the retirement component of that stress is significant.
How to Use This Data
- Find your age row in the tables above
- Choose a realistic spending level for retirement
- Pick a scenario (moderate is recommended for most people)
- Compare to your current investments
- Calculate the gap — that's what you need to close
Or skip all the table-reading and use our Coast FIRE Calculator to get your personalized number in seconds. It adjusts for your exact age, retirement timeline, spending, and market assumptions.
Frequently Asked Questions
Why are the Conservative numbers so high? Conservative assumes only 1% real return (5% minus 4% inflation). At that rate, money barely grows faster than inflation, so you need almost the full retirement amount upfront. Most financial planners consider this overly conservative for a 30+ year timeline.
Which scenario should I use? Moderate (7% return, 3% inflation) aligns with long-term U.S. stock market averages. Use Conservative if you want extra safety margin. Use Aggressive only if you're heavily allocated to equities and comfortable with volatility.
Do these numbers include Social Security? No. These assume you fund retirement entirely through investments. If Social Security exists when you retire, your actual number is lower.
What if I want to retire before 65? Use the calculator — you can set any retirement age. Earlier retirement means a higher Coast FIRE number because your money has less time to grow.