Free Coast FIRE Calculator
Find your exact Coast FIRE number — the amount you need invested today so compound growth alone funds your entire retirement, without saving another dollar. Includes full projection, inflation adjustment, and year-by-year growth table.
| Age | Portfolio Value | Coast FIRE Target | Status |
|---|
How to Use This Coast FIRE Calculator
Four inputs — one powerful answer. Get your complete Coast FIRE picture in seconds.
Set Retirement Spending
Enter how much you want to spend annually in retirement in today's dollars. The calculator adjusts for inflation automatically to show your inflation-adjusted FI number.
Enter Your Ages
Input your current age and the age you want to retire. The gap between these two ages is how long your invested money has to compound before you need it.
Set Return & Withdrawal Rates
Enter your expected annual investment return (historical US market average is ~7% inflation-adjusted) and choose your safe withdrawal rate. The classic 4% rule is pre-selected.
Add Current Savings
Enter your current investment balance to see your progress toward Coast FIRE, how big the gap is, and what year-by-year growth looks like from today.
FIRE Types — Which Path Is Right for You?
Financial Independence, Retire Early (FIRE) comes in several variations — each with different spending targets and lifestyle implications.
Coast FIRE Numbers by Age & Spending Level
Approximate Coast FIRE numbers assuming a 7% annual return and retiring at age 65. Your number changes significantly based on current age and retirement timeline.
| Current Age | Retire at 65 | $40K/yr Spending | $60K/yr Spending | $80K/yr Spending | $100K/yr Spending |
|---|---|---|---|---|---|
| Age 25 | 40 years to grow | $52,641 | $78,962 | $105,282 | $131,603 |
| Age 30 | 35 years to grow | $73,882 | $110,823 | $147,764 | $184,705 |
| Age 35 | 30 years to grow | $103,678 | $155,517 | $207,356 | $259,195 |
| Age 40 | 25 years to grow | $145,492 | $218,238 | $290,984 | $363,730 |
| Age 45 | 20 years to grow | $204,164 | $306,246 | $408,328 | $510,410 |
| Age 50 | 15 years to grow | $286,513 | $429,770 | $573,027 | $716,283 |
* Based on 4% safe withdrawal rate, 7% annual return, and nominal spending (not inflation-adjusted). Use the calculator above for your exact personalized numbers.
Understanding Coast FIRE — The Math Behind Financial Freedom
Coast FIRE is built on two foundational principles: the 4% safe withdrawal rate from the Trinity Study, and the mathematics of compound interest. The FI number — the portfolio size needed for full financial independence — is simply your annual retirement spending divided by your safe withdrawal rate. At 4%, that is 25 times your annual expenses. At 3.5%, it is approximately 28.6 times.
Your Coast FIRE number is the discounted present value of your FI number — how much you need invested today so that compound growth alone reaches your FI number by retirement. The formula is: Coast FIRE = FI Number ÷ (1 + r)^n, where r is your expected annual return and n is years until retirement.
What makes Coast FIRE psychologically powerful is what it unlocks: once you hit that number, you can stop directing income toward retirement savings. Every dollar you earn from that point covers only current expenses — no future obligation. Many people find this milestone more achievable and motivating than full FIRE, and it fundamentally changes their relationship with work.
- Formula based on the Trinity Study's 4% safe withdrawal rate
- Compound interest calculated using standard future value math
- Inflation adjustment uses your entered rate to show real purchasing power
- Withdrawal rate is adjustable — conservative savers can use 3% or 3.5%
- Year-by-year growth table shows every year of your portfolio trajectory
- Progress tracker shows exactly how close you are right now
🔥 Why Coast FIRE Is Different From Regular FIRE
Regular FIRE (Financial Independence, Retire Early) means your portfolio is large enough to support withdrawals right now. Coast FIRE is an earlier milestone — your money is invested and working, but you still need income to cover living expenses. The key difference is that after Coast FIRE, your portfolio is on a self-sustaining growth trajectory toward full FIRE, freeing you from the pressure to save aggressively from every paycheck.
🌡️ Why Inflation Matters So Much in Long-Term Planning
At 3% annual inflation, $50,000 today will require approximately $121,000 in 30 years to buy the same goods and services. This means your FI number must be based on your future inflation-adjusted spending — not today's dollars. Our calculator uses your entered inflation rate to show both the nominal and inflation-adjusted FI numbers, giving you a realistic picture of how large your portfolio needs to be at retirement age.
📈 The Impact of Starting Earlier
The difference between reaching Coast FIRE at 25 versus 35 is dramatic — because you have 10 additional years of compound growth working for you. A $100,000 portfolio at age 25 grows to approximately $1,497,000 by age 65 at 7%. The same $100,000 at age 35 grows to only $761,000. This is why the Coast FIRE number for a 25-year-old is roughly half that of a 35-year-old targeting the same retirement lifestyle — and why starting early is so valuable.
💵 Choosing the Right Safe Withdrawal Rate
The 4% rule from the Trinity Study was based on 30-year retirement periods in US historical market data. If you plan to retire early and have a 40+ year retirement, many financial planners suggest using 3% or 3.5% instead to reduce sequence-of-returns risk. A lower withdrawal rate means a higher FI number — and therefore a higher Coast FIRE number. Use our calculator's withdrawal rate selector to see how this choice affects your target.
Coast FIRE Calculator FAQs
Everything you need to know about Coast FIRE, the math behind it, and how to use this calculator.
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About This Coast FIRE Calculator
This calculator uses the standard FI number formula (annual spending ÷ safe withdrawal rate) and standard present-value discounting (FI Number ÷ (1 + r)^n) to compute your Coast FIRE number. The inflation-adjusted FI number uses your entered inflation rate to project future spending needs. The year-by-year growth table compounds your current balance at the expected return rate and compares it to the Coast FIRE target at each age.
This tool is for educational and planning purposes. Investment returns are not guaranteed — historical market performance does not ensure future results. For personalized retirement planning advice, consult a fee-only certified financial planner (CFP). The 4% safe withdrawal rate is a widely cited guideline, not a guarantee of portfolio survival in all market conditions.
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