Coast FIRE By Age - How much do you need at 25, 35, 45?
Coast FIRE is the point where you have already saved enough that you no longer need to contribute to retirement. Your investments can compound on their own and still reach a full retirement target by traditional retirement age.
If you are new to Coast FIRE, read our introductory post: What is Coast FIRE?.
A common question is:
How much do you need saved by age 25, 35, or 45 to Coast FIRE?
This post gives a practical framework and concrete benchmarks you can compare against. If you want to plug in your own numbers, use the calculator below.
Your FIRE number is $1,500,000, based on $60,000 of annual retirement income and a 4.00% withdrawal rate.
With your current cashflow, you contribute $15,000 per year.
You hit Coast FI at age 37.
That means: if you save until age 37 and then contribute $0 after that, your investments are projected to still reach your FIRE number by age 65.
Real return used: 8.00% (return - inflation).
The Quick Framework
Coast FIRE starts with your retirement target and works backwards.
Step 1: estimate how much you want invested at retirement
Step 2: discount that number back to today using compound growth
A simple retirement estimate:
Retirement number = annual expenses × 25
That assumes a 4% withdrawal rate.
Then:
Coast FIRE number today = retirement number / growth factor until retirement
More years remaining means compounding does more of the work. Fewer years means you need a larger starting balance.
Assumptions for the Examples
To keep comparisons consistent, the examples below assume:
- retirement age: 65
- investment return: 7% real (after inflation)
- withdrawal rate: 4%
- retirement spending: $60,000 per year
That implies a retirement target of:
$60,000 × 25 = $1,500,000
We are asking: how much do you need invested today so it grows to $1.5M without adding more money?
Coast FIRE by Age
Coast FIRE number at 25
Time to grow: 40 years
Growth factor ≈ 15.0×
Needed at 25 ≈ $100,000
Example
- Age 25
- Investments: $100,000
- No new contributions
- Growth: 7% real for 40 years
Result at 65: ≈ $1.5M
This shows how powerful long compounding windows are. The portfolio does most of the work over time.
Coast FIRE number at 35
Time to grow: 30 years
Growth factor ≈ 7.6×
Needed at 35 ≈ $197,000
Example
- Age 35
- Investments: $200,000
- No new contributions
- Growth: 7% real for 30 years
Result at 65: ≈ $1.5M
Ten fewer years of compounding nearly doubles the required starting balance.
Coast FIRE number at 45
Time to grow: 20 years
Growth factor ≈ 3.9×
Needed at 45 ≈ $385,000
Example
- Age 45
- Investments: $385,000
- No new contributions
- Growth: 7% real for 20 years
Result at 65: ≈ $1.5M
As the timeline shortens, the Coast FIRE number rises quickly.
Benchmark Table
| Age | Years to 65 | Coast FIRE number |
|---|---|---|
| 25 | 40 | ~$100,000 |
| 35 | 30 | ~$197,000 |
| 45 | 20 | ~$385,000 |
These numbers scale directly with your retirement lifestyle.
If you want $80k per year instead of $60k, multiply everything by 1.33.
If you want $40k per year, multiply by 0.67.
Key Considerations
Investment returns are uncertain
The examples assume a steady 7% real return. Actual markets are uneven. Some decades outperform, others underperform. A lower long-term return increases the Coast FIRE number.
Many people continue light investing after reaching Coast FIRE to build margin against uncertainty.
Inflation matters
All numbers here are in today’s dollars. The real return assumption already accounts for inflation, but your actual spending may change over time. Lifestyle inflation, housing costs, and healthcare can shift the target.
Retirement age changes the math
If you want to retire at 60 instead of 65, you lose five years of compounding. If you plan to work until 70, the Coast number drops. Even small changes in timeline have a noticeable effect.
Coast FIRE is a milestone, not a finish line
Reaching Coast FIRE does not prevent you from saving more. Many people continue investing because:
- income increases later in their career
- expenses change
- risk tolerance evolves
- goals expand
The Coast number is a useful reference point, not a rule you must follow rigidly.
The calculator above lets you test different assumptions and timelines.
Frequently Asked Questions
Can you Coast FIRE at 25 with $50k?
For most retirement targets, $50k is below the Coast threshold. It is still a strong early foundation and dramatically reduces how much you need to save later.
Do I stop investing after reaching Coast FIRE?
You can, but you don’t have to. Many people continue contributing at a lower rate. Coast FIRE simply means additional saving becomes optional rather than required.
Is Coast FIRE realistic for average earners?
Yes. Coast FIRE relies heavily on time, not extreme income. Consistent investing early in your career has a large long-term impact.
What if my expenses change?
Then the Coast number changes too. Higher retirement spending raises the target. Lower spending reduces it. Revisit your assumptions periodically and update your plan.
If you want to run your own scenario, use the Coast FIRE calculator and model your exact inputs.
This content is for educational purposes only and is not financial, tax, or legal advice. Investing involves risk, including the possible loss of principal. Consider speaking with a qualified professional about your specific situation.