Use this free coast fire calculator to find out how much you need invested today to fund your retirement — without saving another dollar after that point.
Coast FIRE is a financial independence milestone. Your invested assets reach a point where compound interest alone grows them to your retirement goal. No more contributions. No more grinding. Time does the work.
Your coast fire number is not your total net worth. It is one specific figure — the amount you need invested today for your portfolio to reach your retirement target by your chosen age.
Here is a real example. A 30-year-old with $197,000 invested today, at a 7% real annual return, reaches $1.5 million by age 65 without saving another dollar. That is coast fire working exactly as designed.
This is different from traditional FIRE, which demands saving 50 to 70 percent of your income to retire as early as possible. Coast FIRE takes a more balanced path. You keep working to cover today’s expenses. Your retirement is already funded and growing in the background.
Step 1
The gap between these two ages is your compounding window. A 25-year-old needs far less saved than a 40-year-old to hit the same retirement goal. More time means a lower coast fire number.
Step 2
Enter invested assets only. That means your 401(k), Roth IRA, traditional IRA, index funds, ETFs, and taxable brokerage accounts. Do not include your home, car, or emergency fund.
Set monthly contribution to $0 to check if you have already reached Coast FIRE. A green result means you are already there.
Step 3
This drives every number in the calculation. Think housing, food, healthcare, and travel. Be honest with this figure. Underestimating is the most common coast fire planning mistake.
Step 4
The default 7% annual return is the S&P 500 inflation-adjusted average based on historical data from 1926 to 2023. The 4% safe withdrawal rate comes from the 1998 Trinity Study by professors Cooley, Hubbard, and Walz at Trinity University.
Lower these numbers to stress-test your plan. Conservative planners often use 5% to 6% real return to build a buffer.
Step 5
Your results show your coast fire number, your coast fire age, your projected future value, and a savings projection chart. Green means you crossed the threshold. Red means you are still building toward it.
The 4% rule is the foundation of every coast fire calculation. It comes from the 1998 Trinity Study, which analyzed 75 years of S&P 500 and bond market data. The finding: withdrawing 4% of your portfolio annually gives it a very high probability of lasting 30 or more years.
Your retirement target is your annual expenses divided by 0.04. Someone spending $60,000 per year needs $1.5 million invested at retirement.
The coast fire formula works backward from there:
Coast FIRE Number = Retirement Target / (1 + Real Return) ^ Years Until Retirement
At 7% real return, $1 invested at 25 grows to roughly $21 by age 65. That is 40 years of compound interest doing the heavy lifting. All results in this calculator appear in today’s dollars — inflation is already factored in.
Based on Trinity Study data, a 4% withdrawal rate sustains most portfolios for 30 or more years. For early retirees planning a longer retirement, many planners recommend 3% to 3.5% for added longevity.
Your coast fire number changes significantly with age. The table below assumes 7% real return and retirement at 65.
Every five-year delay raises your required coast fire number by roughly 40 percent. A 30-year-old planning $60,000 per year in retirement needs $157,000 today. The same person at 40 needs $308,000. That ten-year gap costs $151,000 in extra required savings.
Run your own numbers using the calculator above.
Crossing the threshold does not mean quitting work tomorrow. It means your retirement is already funded. You work on your terms from this point forward.
Run your own numbers using the calculator above.
The work optional lifestyle becomes real. Take a lower-paying job you enjoy. Go part-time. Change careers. Reduce hours. None of those choices affect your retirement timeline.
Retirement contributions become a choice, not a requirement. Many people keep contributing for extra security. Both approaches work. The key shift is that you only need income to cover today’s living expenses — not to build the retirement nest egg.
Coast FIRE removes retirement saving from your obligations. It does not remove the need to earn. You still need income for rent, food, and healthcare. You stop working to fund retirement. You start working to fund your life. That one change transforms how every workday feels.
Phase 1
Maximize your 401(k) and Roth IRA first. Invest in low-cost index funds and ETFs. Your asset allocation during this phase directly affects how fast you reach your coast fire number. Most planners use 7% real return based on long-run S&P 500 data.
Phase 2
Stop contributing to retirement. Your investment portfolio grows untouched. You earn enough to cover current expenses and nothing more. Compound growth handles the rest while you build a life that actually fits you.
Phase 1 is temporary. That is the entire point. You save aggressively until compound growth takes over. Then it ends for good.
Use 7% as your starting point. It is the S&P 500 inflation-adjusted long-run average. If you want a conservative estimate, use 5% to 6%. The difference in your coast fire number shows you exactly how much buffer you are building in.
Three risks deserve honest attention.
Risk 01
is the most serious. A significant market downturn early in your coasting years can delay your retirement timeline. Keep six to twelve months of living expenses in cash. This prevents a bad market year from pushing you back into aggressive saving.
Risk 02
is expensive. Medicare does not start until 65. Private health insurance can cost $500 to $1,000 per month per person before that. Factor this into your annual expenses from day one.
Risk 03
quietly pushes your spending above your original estimate. Recalculate your coast fire number every year. Adjust when your life changes meaningfully.
Do not panic and restart aggressive saving immediately. First, compare your current portfolio value to your coast fire number using updated return assumptions. If you are still above the threshold, stay the course. If you have dropped below it, a short focused top-up period gets you back on track.
People mix these up because both involve stepping back from aggressive saving. The difference is straightforward.
In Coast FIRE, your retirement is fully funded and growing without contributions. You work to cover today’s expenses only. In Barista FIRE, your savings only partially cover retirement. You still need part-time income, often for health insurance benefits, to bridge the remaining gap.
In Lean FIRE, you are fully retired on a strict minimal budget with no work required.
If you want flexibility, a normal lifestyle, and retirement secured on your own timeline, Coast FIRE is the right fit.
Scenario 1
$100,000 at 7% real return over 37 years becomes $1.4 million by age 65. For $50,000 annual retirement spending, the coast fire number is $104,000. This person has already crossed the threshold. Phase 2 starts now.
Scenario 2
Retirement target at $70,000 annual spending is $1.75 million. Coast fire number at 7% over 30 years is $230,000. They are $30,000 away. At their current savings rate, they hit the milestone in under two years.
Scenario 3
Yes. Absolutely. Scenario 3 proves it. Targeting $60,000 annual retirement spending means needing $1.5 million. Coast fire number at 7% over 25 years is $308,000. This person is just $8,000 away. Starting late makes Phase 1 shorter and more focused. It does not make coast fire impossible.
