Coast FIRE (or "coast FI") is one of the most freeing milestones in the whole FIRE movement. It is the point at which the money you have already saved is large enough that, even if you never contribute another dollar, it will grow on its own into the nest egg you need by the time you reach a normal retirement age. Once you are coasting, you are free to take a lower-paying, lower-stress, or more meaningful job — because the finish line is already locked in.
This calculator answers a single question: is your current balance already on autopilot to your retirement number? You enter your age, what you have saved, when you want to retire, a reasonable growth rate, and the nest egg you need. It then tells you your "coast FIRE number" — the balance you needed today — and whether you have already reached it.
How to Use
- Enter your Current Age — how old you are today. This anchors how many years your money has left to compound.
- Enter your Current Retirement Savings — the total you already have invested across 401(k), IRA, brokerage, and similar accounts. Include old 401(k)s you have forgotten about.
- Set your Planned Retirement Age. Sixty-five is the default, but many FIRE planners use 60, 62 (Social Security eligibility), or 55 (rule-of-55 access).
- Enter your Expected Annual Return. A diversified portfolio historically averages about 7% after inflation when held long enough. Use a more conservative 5–6% if you want a safer estimate.
- Enter your Target Nest Egg at Retirement. The standard way to find it is to divide your annual retirement spending by the 4% safe withdrawal rate — for example, $60,000 a year divided by 0.04 equals a $1.5 million target.
The result card then compares two figures: what your existing savings will grow to by retirement, and the target you need. If the projected balance is at or above the target, you are already coasting and can stop saving for retirement entirely.
The Math Behind Coast FIRE
Coast FIRE is just a future-value problem run in reverse. Your savings today need to compound forward to your target:
projectedBalance = currentSavings × (1 + r)^yearsToRetirement
To find the balance required today, rearrange it:
coastFireNumber = targetNestEgg ÷ (1 + r)^yearsToRetirement
Where r is your expected annual return and yearsToRetirement is your planned retirement age minus your current age. The power comes entirely from the exponent: the earlier you are, the smaller the balance you need, because time does the heavy lifting.
Worked example on the default numbers: age 35, $200,000 saved, retiring at 65 at a 7% return. That is 30 years to compound, and (1.07)^30 ≈ 7.61. So $200,000 grows to about $1,522,451 — which already clears the $1.5 million target. The coast FIRE number today is only $197,051. Because the saver already has $200,000, they have already crossed the line: no further retirement contributions are required.
If the return is 0%, growth does nothing, so the coast FIRE number equals the full target — meaning you have to save the whole thing yourself. That is why a positive long-run return assumption matters so much.
What Changes When You Go Coast
Reaching coast FIRE is not the same as being financially independent. You cannot stop working tomorrow; you still need income to cover living expenses between now and retirement. What changes is that you no longer need to save for retirement. The future number is taken care of, so every new dollar you earn can go toward current life: paying off the house, travel, family, or simply working fewer hours.
People use coast FIRE to switch careers, go part-time, start a business, or take a dream job that pays less. It is a psychological release as much as a financial one — the "what if I never retire?" anxiety is gone, because the math already works.
Examples
Example 1 — Already coasting (the default). At age 35 with $200,000, a 7% return and a $1.5 million target at 65, the projected balance is about $1,522,451, above target. The calculator reports a $0 gap and "already coasting." This person can pause 401(k) contributions and redirect the money elsewhere.
Example 2 — A long runway ahead. At age 25 with only $10,000 saved, aiming for $1.5 million at 65 (40 years) at 7%, the projected balance is roughly $149,745, far below target. The coast FIRE number today is about $100,171, leaving a gap of about $90,171. On current savings alone, reaching coast FIRE would take roughly 74 years — meaning this saver must keep contributing steadily.
Example 3 — A very large nest egg. At age 40 with $1,500,000 already invested and a $2,000,000 target at 65 (25 years), the balance compounds to about $8.14 million at 7%. The coast FIRE number today is only $368,498, so this person is deeply coasting with a large margin of safety.
FAQ
What is Coast FIRE in simple terms?
Coast FIRE is the milestone where the money you have already saved will, by itself, grow into your retirement nest egg by the time you retire. After you hit it, you do not need to save any more for retirement — your existing balance is "on autopilot." You still work to cover living costs, but the future number is locked in.
How is the coast FIRE number calculated?
Take your target nest egg at retirement and divide it by (1 + expected return) raised to the number of years until retirement. For example, a $1.5 million target, 30 years to retirement, and a 7% return gives 1,500,000 ÷ (1.07)^30 ≈ $197,051. If you already have at least that much invested today, you are coasting.
Is Coast FIRE the same as retiring early?
No. Coast FIRE means your future retirement is funded, but you still need income to live on between now and retirement. Full FIRE means you can stop working entirely today. Coast FIRE lets you downshift or switch jobs; true FIRE lets you stop working altogether.
What return assumption should I use?
A long-run diversified stock-and-bond portfolio historically returns roughly 7% after inflation. If your timeline is shorter or your allocation is conservative, use 5–6% to avoid overestimating. Lowering your assumed return raises the coast FIRE number you need today.
How do I find my target nest egg?
Use the 4% rule: divide your expected annual retirement spending by 0.04. If you want $60,000 a year in retirement, your target is $60,000 ÷ 0.04 = $1.5 million. Adjust for pensions, Social Security, and any guaranteed income you expect.
What if the projected balance already exceeds my target?
Congratulations — you are already coasting. The gap to coast FIRE is $0 and further retirement saving is optional. You can redirect future savings to paying down debt, investing in a home, travel, or simply lowering your work hours without jeopardizing your retirement.
Disclaimer
This Coast FIRE calculator is provided for informational purposes only and does not constitute financial, investment, or tax advice. Projections rely entirely on the return rate and inputs you enter; actual market returns are variable and sequence-of-returns risk, inflation, and taxes are not modeled. The 4% rule is a guideline, not a guarantee. Always build a broader plan with a qualified financial professional before making major career or retirement decisions.