You’ve been investing for years. The portfolio is growing. And somewhere in the back of your mind is a question you’ve never quite answered: could I stop contributing right now — and still make it?
That’s the Coast FIRE question. And this coast fire calculator is built to answer it. Enter your numbers, get your Coast FIRE number, and find out whether compound growth alone will carry you to financial independence from here.
What Is Coast FIRE?
Coast FIRE is the point where your current invested portfolio, left untouched and given enough time to compound, will grow to your full FIRE number by retirement — without a single additional contribution.
You’ve done the hard part. The math takes it from here.
If you want a deeper breakdown of how Coast FIRE fits alongside Lean FIRE, Barista FIRE, and Fat FIRE, the 4 Types of FIRE article covers each in full. What you need here is the number.
How to Use This Calculator
Five inputs. Each one matters.
Current age and target retirement age — These define your time horizon, which is the single biggest lever in the calculation. An extra five years of compounding can dramatically lower the amount you need today.
Current invested assets — This is your portfolio: 401(k), IRA, brokerage accounts, HSA invested in the market. Do not include your emergency fund, home equity, or cash savings. Coast FIRE is specifically about invested assets working through compound growth.
Monthly expenses in retirement — What you expect to spend each month when you’re no longer working. The calculator multiplies this by 12, then by 25 (the 4% rule multiple) to determine your FIRE target. If you’re not sure of this number, use your current monthly spending as a starting point — many people spend less in retirement, but it depends heavily on your plans.
Expected annual return — The calculator defaults to 7%, which is the approximate real (inflation-adjusted) return of the S&P 500 over the long term. According to data compiled by NYU Stern and Trade That Swing, the inflation-adjusted 30-year average annual return of the S&P 500, including dividends, has been approximately 7.4%. A 7% default is therefore a reasonable, slightly conservative real-return assumption for a diversified equity portfolio.
Using a real return means your Coast FIRE number is already expressed in today’s dollars. You don’t need to adjust separately for inflation. This is the same methodology used across the FIRE Calculator on this site, and it’s explained in more detail below.
The Coast FIRE Formula
The calculation behind the calculator is straightforward:
Coast FIRE Number = FIRE Target ÷ (1 + r)^t
Where:
- FIRE Target = annual retirement expenses × 25
- r = annual return rate (as a decimal)
- t = years until target retirement age
Working through an example: suppose you’re 35, you plan to retire at 60, your monthly expenses are $4,000, and you’re using a 7% real return.
- FIRE target: $4,000 × 12 × 25 = $1,200,000
- Growth factor: (1.07)^25 = approximately 5.43
- Coast FIRE number: $1,200,000 ÷ 5.43 = approximately $221,000
If you have $221,000 invested today at 35, compound growth alone — with no further contributions — projects to reach $1,200,000 by age 60.
That’s the power the calculator is surfacing. The reason this number is so much lower than the FIRE target is compound interest: 25 years of growth at 7% more than quintuples the original investment.
What the Results Mean
Your Coast FIRE Number
This is the amount your invested portfolio needs to be today for compounding to reach your FIRE target by your target retirement age — assuming your chosen return rate and no further contributions.
Your FIRE Number
Annual expenses × 25. This is the total portfolio you need at retirement to sustain withdrawals indefinitely at a 4% annual rate. The 4% rule traces back to research by William Bengen (1994) and the subsequent Trinity Study (1998), which examined historical portfolio survival rates across 30-year retirement periods.
Projected Portfolio at Retirement
What your current investments are projected to grow to by retirement age, at the return rate you entered — again, with zero additional contributions. If this number exceeds your FIRE target, you’ve crossed Coast FIRE.
The Progress Bar
Shows where your current portfolio sits relative to your Coast FIRE number. At 100%, you’ve reached it.
The Retirement Age Sensitivity Table
The calculator also generates a table showing your Coast FIRE number at retirement ages from your nearest 5-year increment up to 70, with your target highlighted.
This table answers a question that comes up often: what if I pushed retirement back slightly? Coast FIRE numbers fall quickly as the retirement age increases, because each additional year of compounding shrinks how much you need today. For readers who are close but haven’t crossed the line, the sensitivity table often reveals that a two- or three-year adjustment to their timeline already puts them there.
What to Do With Your Result
Branch A: You’ve Reached Coast FIRE
If your current investments already exceed your Coast FIRE number, the math says you’re done with the retirement-savings part of the equation. Compound growth will handle it from here.
What that means in practice depends entirely on what you want to do with that information.
Some people discover they’ve crossed Coast FIRE and choose to stay in their current role anyway — contributions now are going toward early retirement, not just retirement, and the gap between their Coast number and full FIRE closes faster with continued investing. That’s a completely valid choice. Coast FIRE crossing doesn’t mean you must stop contributing; it means you no longer have to.
Others use it as the permission slip they needed to make a change they’d been putting off. That might be stepping back to part-time work, moving to a career that pays less but asks more of them in the right ways, or launching something on their own terms knowing that retirement is no longer contingent on the venture succeeding. The calculation doesn’t prescribe a lifestyle. It removes a financial constraint and hands the decision back to you.
A common bridge strategy is Barista FIRE: working part-time or in a lower-stress role that covers current expenses while your portfolio grows untouched. If you’ve reached Coast FIRE, Barista FIRE is a realistic near-term option, not a distant aspiration. The article on Barista FIRE jobs covers specific roles and income targets worth knowing before you make a move.
One note worth making: reaching Coast FIRE does not mean retirement is certain. The projection depends on your return assumption holding over the remaining time horizon. Markets don’t return 7% every year — that’s a long-run average that includes some steep and extended losses. Most planners suggest continuing to track your net worth and revisiting the calculation periodically, particularly after a major market downturn or a significant life change (new dependents, a move to a higher cost-of-living area, a shift in planned retirement spending).
If you want to model what happens if returns come in lower than expected, or scenario-test different retirement ages, [ProjectionLab] [AFFILIATE PLACEHOLDER — ProjectionLab] is built specifically for this kind of what-if planning. Being able to stress-test the projection is worth doing before making any irreversible career decisions.
For a broader view of what early retirement actually looks like once you get there — the practical, psychological, and financial realities — that article is worth reading before committing to a timeline.
Branch B: You Haven’t Reached Coast FIRE Yet
The gap between your current portfolio and your Coast FIRE number tells you how far to go. But the more useful question is: which input moves the number the most, and which lever is actually within your control?
Time horizon: Pushing your target retirement age out by five years lowers your Coast FIRE number substantially — often by 25–35% depending on your return assumption. This isn’t about giving up on an earlier retirement; it’s about understanding what a modest adjustment to the timeline is worth in terms of required starting capital. The sensitivity table in the calculator shows exactly how much, at your specific inputs. For many readers who are $30,000–$50,000 short of their Coast FIRE number, a three-year target adjustment resolves the gap entirely.
Return rate: Higher assumed returns reduce your Coast FIRE number. A difference of one percentage point in the assumed return rate, compounded over 25 years, changes the required starting amount by roughly 20%. The direction cuts both ways: more aggressive assumptions carry more risk, and a plan built on 9% real returns has less margin for error than one built on 7%. For planning purposes, erring conservative is generally sound.
Savings rate: The fastest way to close the gap is to increase contributions now. The savings rate article covers the math in detail, including how different contribution levels map to timeline acceleration. A reader currently investing $1,000/month who increases to $1,500/month doesn’t just save more — they compress the time to Coast FIRE because every additional contributed dollar arrives with more years of compounding ahead of it.
FIRE target: If your monthly expense estimate feels inflated — or if your actual retirement spending would genuinely be lower than today — revisiting that input reduces your FIRE target and, in turn, your Coast FIRE number. A $500/month reduction in planned retirement spending lowers the FIRE target by $150,000 (at the 25x multiplier), which significantly reduces the Coast number too.
If you’re not yet investing consistently or need to set up the accounts to do so, the how to start investing guide covers the foundational steps.
The “What if I keep contributing?” section in the calculator lets you model the impact of a monthly contribution directly: it shows your projected total at retirement with contributions added, and calculates how many years earlier you’d hit your full FIRE number if you maintained that pace. For readers who are close to Coast FIRE, this tool is particularly useful — it shows the marginal value of continued contributions even after you’ve crossed the threshold.
[Empower] [AFFILIATE PLACEHOLDER — Empower] offers free net worth tracking and portfolio monitoring, which is useful for staying on top of where you stand relative to your Coast FIRE number over time as your portfolio grows.
Coast FIRE Numbers by Age: Reference Points
Because time is the dominant variable, Coast FIRE numbers vary enormously by age. The table below uses a $1,200,000 FIRE target and a 7% real return to give a sense of scale:
| Age | Years to Age 60 | Coast FIRE Number |
|---|---|---|
| 30 | 30 | ~$157,000 |
| 35 | 25 | ~$221,000 |
| 40 | 20 | ~$311,000 |
| 45 | 15 | ~$438,000 |
| 50 | 10 | ~$610,000 |
Based on a $1,200,000 FIRE target ($4,000/month in retirement) and 7% real annual return. For illustration only — past performance does not guarantee future results.
Two things stand out in this table. First, the numbers at 30 and 35 are lower than most people expect — which is why many readers running this calculator for the first time discover they’re closer than they thought. Second, each five-year delay roughly doubles the required starting amount. This is the math that makes early investing so valuable: not because returns are guaranteed, but because time doing the work is irreplaceable.
The calculator handles your specific inputs. Use the table as a gut-check before you run the numbers.
Real Returns vs. Nominal Returns: Why It Matters
The calculator uses real returns by default — that is, returns already adjusted for inflation. This is worth understanding because different calculators handle this differently, and it changes the result significantly.
A nominal return of 10% with 3% inflation is a real return of roughly 7%. If you plug a 10% nominal return into a calculator that doesn’t adjust for inflation, you’ll get a Coast FIRE number expressed in future (inflated) dollars — which looks lower than it actually is in today’s purchasing power. If you plug 7% into a calculator using real returns, you get a Coast FIRE number in today’s dollars, which is directly comparable to your current portfolio.
The site’s standard across calculators is real returns, because it means you’re comparing apples to apples: today’s portfolio value against a Coast FIRE number expressed in today’s dollars.
If you choose to enter a nominal return instead, your result will be expressed in future dollars and will require a separate mental adjustment for inflation. For most readers, the default 7% real return produces the most interpretable result.
Conclusion: Key Takeaways
Coast FIRE is worth calculating for one specific reason: most people who’ve been investing for several years have no idea whether they’ve crossed it. A single run of this calculator changes that.
- The formula: Coast FIRE number = FIRE target ÷ (1 + r)^t
- The default return: 7% is a real (inflation-adjusted) rate, consistent with long-run S&P 500 historical data. Your result is in today’s dollars.
- The two outcomes: If you’ve reached Coast FIRE, contributions are optional — what you do with that information is a lifestyle question. If you haven’t, the sensitivity table and the “keep contributing” module show you exactly which levers to pull.
- The limits: This is a projection, not a guarantee. Return assumptions carry uncertainty over long time horizons. Revisit the calculation as your portfolio and plans evolve.
Once you have your Coast FIRE number, the FIRE Calculator shows where you stand on your full FIRE timeline — including how long until you could retire entirely if you kept contributing at your current rate.
FAQ
What return rate should I use in the Coast FIRE calculator?
The calculator defaults to 7%, which represents the approximate real (inflation-adjusted) annual return of the S&P 500 over the long run, based on data extending back to 1957. A 7% real return is a reasonable baseline for a diversified equity portfolio. More conservative investors sometimes use 5–6%; more aggressive assumptions go up to 8–9% real. The lower your assumed return, the higher your Coast FIRE number — which is the direction you want to err if you’re building a plan you need to rely on.
Should I use a nominal or real (inflation-adjusted) return rate?
Use a real return rate. The calculator is designed around real returns, meaning your result is expressed in today’s dollars. This makes it directly comparable to your current portfolio. If you enter a nominal rate (say, 10%), your Coast FIRE number will be understated because it won’t account for inflation eroding your future purchasing power. The 7% default already factors inflation in — you don’t need to adjust separately.
What’s my FIRE target — and how does it affect my Coast FIRE number?
Your FIRE target is annual retirement spending × 25. It’s derived from the 4% rule: if you withdraw 4% per year from your portfolio, a $1,000,000 portfolio sustains $40,000 in annual withdrawals. The 25x multiplier is simply the inverse of 4%. Your FIRE target feeds directly into your Coast FIRE number — a higher target requires a higher Coast FIRE number. The most common way to lower both is to plan for lower retirement expenses, either through genuine lifestyle flexibility or by factoring in paid-off housing or other reduced costs in retirement.
How is Coast FIRE different from Barista FIRE?
Coast FIRE is a portfolio milestone: your investments can reach your full FIRE target through compounding alone. Barista FIRE is a lifestyle strategy: you’ve accumulated enough that you only need part-time income to cover current expenses while your portfolio continues to grow. You can be at Barista FIRE without having reached Coast FIRE, and vice versa. The two concepts often overlap — many people who’ve reached Coast FIRE shift to a Barista FIRE arrangement as a practical next step.
Does my Coast FIRE number change if I retire later?
Yes, meaningfully. Every additional year of compounding reduces the amount you need today. The sensitivity table in the calculator shows your Coast FIRE number at five-year intervals up to age 70. For most inputs, pushing the retirement target five years later lowers the required Coast FIRE number by roughly 25–30%.
Should I include Social Security in my Coast FIRE calculation?
It depends on how conservative you want to be. Social Security reduces your required retirement spending from your portfolio, which lowers your FIRE target and, in turn, your Coast FIRE number. Many FIRE planners exclude Social Security entirely from the base calculation and treat any future benefit as a buffer. Others include a portion — particularly those planning to retire at 60 or later, where Social Security eligibility is closer. If you include it, reduce your monthly retirement expense input by your estimated monthly Social Security benefit, then run the calculator. The result will reflect a lower FIRE target and a lower Coast FIRE number.