This Coast FIRE calculator finds your coast fire number — the amount you need invested today so that compound growth alone, with no further contributions, carries you to a fully funded retirement. Once you cross that line, you only need to earn enough to cover current living expenses and can let the portfolio “coast.”
Enter your age, target retirement age, current investments, and expected spending, and the calculator computes your coast number, your full FIRE number, and the verdict: are you coasting yet? If not, it estimates the age you could stop contributing based on what you invest each year.
What Coast FIRE Means and How the Number Is Calculated
Coast FIRE (also written Coast FI) is a milestone on the road to financial independence. The math runs in three steps:
1. FIRE number today = Annual retirement spending ÷ Safe withdrawal rate. Spending $40,000 at the 4% rule means $1,000,000 in today’s dollars. 2. Inflate to retirement: at 3% inflation over 35 years, that $1,000,000 becomes about $2.81 million nominal. 3. Discount back at your expected return: your coast number = FIRE number ÷ (1 + real return)^years, where the real return strips inflation out of your nominal return ((1.07 ÷ 1.03) − 1 ≈ 3.88%).
If your invested balance already meets the coast number, time and compounding finish the job without another dollar saved.
Worked Example: A 30-Year-Old with $100,000
Take a 30-year-old planning to retire at 65 on $40,000 per year (today’s dollars), assuming a 7% return, 4% withdrawal rate, and 3% inflation.
- FIRE number: $40,000 ÷ 0.04 = $1,000,000 today, about $2.81M in 2061 dollars.
- Coast FIRE number at 30: roughly $263,600.
- With $100,000 invested, the shortfall is about $163,600 — not coasting yet.
- Contributing $15,000 per year, the projection crosses the coast line around age 52; from there, growth alone reaches the full FIRE number by 65.
Every year you wait, the coast number rises by the real return (~3.9% here), which is why the target is dramatically lower at 25 than at 45.
Barista FIRE and Other Variants
Coast FIRE has a popular cousin. Barista FIRE means your portfolio is large enough that part-time work — the stereotypical coffee-shop job with health insurance — covers your living costs while investments grow untouched. A barista fire calculator run is just this tool with an earlier “stop contributing” date plus a plan for part-time income and, crucially, health coverage before Medicare at 65.
Other waypoints on the same spectrum:
- Lean FIRE: full independence on frugal spending (often under $40,000/yr).
- Fat FIRE: independence at $100,000+/yr spending.
- Full FIRE: portfolio covers everything — work becomes optional.
Coast FIRE is usually the first milestone reached, and hitting it often changes career decisions more than the final number does.
Frequently Asked Questions
What is a Coast FIRE number?
Your Coast FIRE number is the invested amount that, left alone with no further contributions, compounds into a fully funded retirement by your target age. It equals your FIRE number (annual spending ÷ safe withdrawal rate) discounted back to today at your real expected return. A 30-year-old targeting $1M in today’s dollars at 65 needs roughly $260,000 invested.
How do I calculate Coast FIRE?
Divide annual retirement spending by your safe withdrawal rate to get your FIRE number, then divide by (1 + real return) raised to the years until retirement. Example: $40,000 ÷ 0.04 = $1,000,000; with a ~3.9% real return and 35 years, $1,000,000 ÷ 1.039^35 ≈ $262,000. Invested today, that sum coasts to the goal.
What is the difference between Coast FIRE and Barista FIRE?
Coast FIRE means you have enough invested that you can stop contributing and still retire fully on schedule — you just need income for current expenses. Barista FIRE is living that plan via part-time work, often chosen for employer health insurance. Coast FIRE is a savings milestone; Barista FIRE is a lifestyle built on top of it.
What is the 4% rule?
The 4% rule says a retiree can withdraw 4% of their portfolio in year one, adjust that amount for inflation annually, and historically not run out of money over a 30-year retirement. It comes from the 1994 Bengen study and the Trinity study. Inverted, it means you need about 25 times your annual spending invested.
How much do I need to Coast FIRE at 30?
For a $40,000-per-year retirement at 65, roughly $260,000–$270,000 invested at age 30 (assuming a 7% return, 3% inflation, 4% withdrawal rate). Spending $60,000 pushes it near $395,000; retiring at 60 instead of 65 raises it further. Run your own spending, ages, and return assumptions above — the number is very sensitive to them.