Meet the Coast FI Calculator: The Number That Changes How You Think About Work

Full FIRE means quitting forever. Coast FIRE means something more flexible: your retirement is already funded by existing investments — you just need to cover your living expenses until retirement age. No more retirement contributions. Every dollar you earn from now on goes to the present, not the future.

Alistair's Coast FI Calculator finds that number and shows what it unlocks.

What Coast FI Means

You've hit Coast FI when your current investments, left to grow at a reasonable return until your full retirement age, will reach your FI number — without you adding another dollar.

Example: You're 35, you have $250,000 invested, your FI number is $1,500,000, and you plan to fully retire at 65. At 7%, $250,000 grows to roughly $1,900,000 in 30 years — well above the $1.5M target. You've hit Coast FI. You can stop contributing to retirement accounts entirely and redirect that money to whatever matters now.

What Changes at Coast FI

• You can take a lower-paying job you actually enjoy
• You can go part-time, freelance, or start a business
• You can spend more on travel, family, or hobbies today — because tomorrow is already covered
• You can stop stressing about the market — your timeline is long enough that short-term volatility doesn't matter

Coast FI doesn't mean you stop working. It means work becomes optional — you're working for the present, not the future.

What the Tool Calculates

The microtool takes your current age, net worth, annual expenses, target retirement age, and expected return — then computes:

• Your Coast FI number: How much you need invested today to hit your FI number by retirement age with zero additional contributions
• Current status: Whether you've reached Coast FI
• Coast FI age: If you haven't hit it yet, when you will (given your current savings trajectory)
• Monthly savings needed: If not at Coast FI, how much to save per month to get there

Real Numbers: Coasting at 35 vs. 45

Alex, age 35:

• Net worth: $250,000
• FI number: $1,500,000 ($60K × 25)
• Target retirement: 65 (30 years)
• Expected return: 7%

$250,000 × (1.07^30) ≈ $1,903,000 — over the $1.5M target. Coast FI reached.

Alex can stop retirement contributions now and spend the next 30 years earning just enough to cover current expenses. The retirement fund is on autopilot.

Jordan, age 35:

• Net worth: $100,000
• FI number: $1,500,000
• Target retirement: 65 (30 years)

$100,000 × (1.07^30) ≈ $761,000 — well short. Not yet at Coast FI.

The tool calculates: Jordan needs to save roughly $1,100/month for the next 8 years to hit Coast FI by age 43. After that, no more retirement contributions are needed. Coast FI at 43 — that's 22 years of working for the present.

Why Coast FI Changes the Game

Full FIRE requires saving aggressively for decades. Most people can't or won't save 50%+ of their income. Coast FI gives you the best of both worlds: your future is secured, but you're not living on rice and beans to get there. You just need to let time do its job.

Alistair shows you when you can stop the retirement sprint and start coasting.

That's what this microtool does. Find your Coast FI moment — it's probably closer than you think.