Coast FIRE Calculator

Coast FIRE is a financial milestone that means you have saved enough money that compound growth alone will carry your portfolio to your retirement target — without contributing another dollar. Once you reach your Coast FIRE number, you only need to earn enough to cover your current living expenses, freeing you to pursue lower-paying but more fulfilling work, reduce your hours, or take career risks without worrying about retirement savings.

How the Coast FIRE Number Is Calculated

Your Coast FIRE number is determined by working backward from your target retirement portfolio. Start with your FIRE number: annual retirement expenses divided by your safe withdrawal rate (typically 4%). If you plan to spend $50,000 per year in retirement, your FIRE number is $50,000 / 0.04 = $1,250,000. Next, discount that amount back to today using your expected investment return and the number of years until retirement.

The formula is: Coast FIRE Number = FIRE Number / (1 + r)^n, where r is your expected annual return and n is years to retirement. At a 7% return with 30 years to go, your Coast FIRE number is $1,250,000 / (1.07)^30 = $164,178. Once your savings exceed $164,178, you can stop contributing and compound growth handles the rest.

The numbers are surprisingly attainable for young savers. A 25-year-old targeting $50,000 in annual retirement spending at age 60 (35 years away) needs only about $115,000 saved to reach Coast FIRE at a 7% return. This is achievable within 5-8 years of aggressive saving after college.

Coast FIRE vs Regular FIRE: Understanding the Difference

Regular FIRE (Financial Independence, Retire Early) means your portfolio is large enough to cover your expenses indefinitely through withdrawals. You can stop working entirely. Coast FIRE is a halfway point — you have saved enough for retirement but still need income to cover today's bills. Think of it as financial security rather than full financial independence.

The practical difference is life-changing. At Coast FIRE, every dollar you earn goes to current expenses and lifestyle — none needs to go to retirement accounts. This opens up options: switch to part-time work, take a lower-paying dream job, start a business without the pressure to replace your full income, or take a gap year. Your retirement is already handled by your existing savings.

What Assumptions Does Coast FIRE Depend On?

Coast FIRE is only as reliable as its assumptions. The standard 7% return reflects the historical real (inflation-adjusted) return of the US stock market. More conservative investors should use 5-6% to build in a safety margin. Your target retirement spending might also change — lifestyle inflation, healthcare costs, or relocating to a high-cost area could increase your FIRE number. Use our calculator above to model different scenarios, and check your compound interest projections to visualize how your current savings grow over time. Consider also running your numbers through our 401(k) contribution calculator to optimize the tax efficiency of your savings.

Reaching Coast FIRE in your 20s or 30s is one of the most powerful financial moves a young person can make. The mathematics of compound interest heavily favor early savers — someone who saves aggressively for 5-10 years in their 20s can stop retirement contributions entirely and still retire comfortably, while someone who starts at 35 may need to save for 20+ years to reach the same result.

Coast FIRE Savings Targets by Age

The amount you may want to reach Coast FIRE varies dramatically based on your current age and target retirement age. At age 25 targeting retirement at 60 with $50,000 annual expenses (4% withdrawal rate, 7% return), your Coast FIRE number is approximately $115,000. At age 30, it rises to $161,000. At 35, it is $226,000. Every five years of delay roughly increases your target by 40%, which is why starting early matters so much.

To hit $115,000 by age 25, starting from zero at age 22, you would need to save about $2,900 per month for three years — aggressive but feasible with a high-paying tech or finance job and low expenses. A more realistic path is saving $1,500 per month from age 22 to 28, reaching roughly $120,000 with market growth. Max out your 401(k) if your employer offers a match, since the match accelerates your timeline by 25-50%.

The Best Accounts for Building Your Coast FIRE Portfolio

Prioritize tax-advantaged accounts for your Coast FIRE savings. A 401(k) with employer match is the first stop — that match is free money that cannot be beaten. Next, fund a Roth IRA (or backdoor Roth if your income is too high) for tax-free growth. If you have maxed both, use an HSA if you have a high-deductible health plan — the triple tax advantage makes it the most tax-efficient account available. Only after maxing these should you use taxable brokerage accounts.

For investment allocation during the accumulation phase, a simple three-fund portfolio (total US stock market, international stocks, and bonds) with a heavy equity tilt (80-90% stocks) is appropriate for young Coast FIRE seekers. The long time horizon (25-35 years to retirement) smooths out short-term market volatility. Target-date funds are a reasonable set-it-and-forget-it option that automatically shift toward bonds as retirement approaches.

Life After Reaching Coast FIRE: What Changes

Reaching Coast FIRE does not mean you have to stop saving — it means you have the option to stop. Many people who hit Coast FIRE continue contributing but with reduced intensity, channeling the freed-up cash flow toward travel, hobbies, a home purchase, or starting a business. The psychological shift is significant: knowing your retirement is secure removes the anxiety that drives many career decisions. You can evaluate job opportunities based on fulfillment and growth rather than purely on salary. Use our calculator to find your exact Coast FIRE number, then track your compound growth trajectory to see when you may cross the finish line.

The return rate assumption in your Coast FIRE calculation is the single most impactful variable — small changes compound over decades to create massive differences in your target number. Using 8% versus 6% can change your Coast FIRE number by 40% or more. Choosing the right return rate is not about precision; it is about building in enough margin of safety that your plan survives real-world volatility.

Historical Investment Returns and What They Mean for Coast FIRE

The S&P 500 has returned approximately 10% annually in nominal terms (before inflation) and about 7% in real terms (after inflation) since 1926. This 7% real return is the most commonly used assumption in FIRE calculations. However, this average masks enormous variation: decade-long periods have produced real returns ranging from -1% to 13%.

For Coast FIRE planning, use real (inflation-adjusted) returns so that your target is in today's dollars. If you use nominal returns, you may want to inflate your target retirement spending as well, adding unnecessary complexity. A 7% real return is reasonable for a portfolio of 80-90% US stocks, but consider that many financial planners now project 5-6% real returns for the next decade due to elevated valuations. Using a lower return rate means a higher Coast FIRE number but a more robust plan.

Conservative vs Aggressive Return Rate Assumptions

Running your calculation at multiple return rates reveals the sensitivity of your Coast FIRE plan. For a 30-year-old targeting $1,250,000 at age 65, the Coast FIRE number at 7% is $161,000, at 6% it is $209,000, and at 5% it is $271,000. The difference between the optimistic and conservative scenarios is $110,000 — a significant amount that could represent two to three additional years of aggressive saving.

A prudent approach is to plan at 5-6% and treat anything above that as a bonus. If markets perform at the historical 7% average, you may reach your goal ahead of schedule and have options: retire earlier, spend more in retirement, or leave a larger inheritance. If markets underperform, your conservative target protects you from running short.

How the Safe Withdrawal Rate Interacts With Your Coast FIRE Number

The 4% withdrawal rate (based on the Trinity Study) assumes a 30-year retirement. If you plan to retire at 50 with a 40+ year retirement, consider using 3.5% instead, which increases your FIRE number and consequently your Coast FIRE target. Conversely, if you expect significant Social Security or pension income, you might use a higher withdrawal rate for the gap years before those benefits kick in. Model different scenarios with our calculator above, adjusting both the return rate and withdrawal rate to stress-test your Coast FIRE plan. You can also visualize the growth trajectory with our compound interest calculator to see how your current savings compound under different return assumptions.