Coast FIRE Calculator

Find the amount you need invested today so your portfolio can grow (without further contributions) to your FI number by your target retirement age. Optionally see how long it takes to “hit coast” with ongoing monthly contributions.

Your expected yearly expenses in retirement (real, today’s dollars).
Common picks: 3.5–4.5%. FI number is Annual / (SWR/100).
Age when you plan to stop working.
Used to compute years until retirement.
After inflation. Typical long-term stock/bond mixes: ~3%–7%.
Tax-advantaged + taxable investment balances earmarked for retirement.
Used to estimate when you’ll reach “coast” if not already there.
Click an example to auto-fill and see results immediately.
Shows: FI number, years to retirement, Coast amount today, and the time-to-coast condition B(t) ≥ P_needed(t) with your inputs substituted.

Result

FI Number

—
Target portfolio: FI = Annual / (SWR/100).

Coast Needed Today

—
P_needed = FI / (1 + r)^years, where r is real return.

Status

—
Whether your current investments already meet today’s Coast requirement.

If Not Coasted: Time to Hit Coast with Contributions

—
Estimates the first month t where your balance meets the moving Coast requirement.
Helping notes:
  • Real return means after inflation. If you input a nominal return, your FI number should be in nominal terms too.
  • Without contributions, if you aren’t coasted now, you won’t “catch up” later—both your balance and the Coast requirement grow at the same rate.
  • SWR is an assumption (often 3–5%). Lower SWR → larger FI number → higher Coast requirement.
  • This tool ignores taxes, fees, sequence risk, and glide-path changes. Treat results as planning estimates, not advice.

What is a Coast FIRE Calculator?

A Coast FIRE Calculator shows how much you must have invested now so that, without making any future contributions after a chosen “coast” point, compound growth alone carries you to financial independence at retirement. In Coast FIRE, you cover current living expenses from work you enjoy, then stop aggressive saving once your portfolio can grow itself to the goal. The goal is typically a multiple of annual expenses (e.g., the “25× rule”), optionally adjusted for inflation. By combining expected investment returns with inflation assumptions, the calculator translates your independence target into a required “present balance” that can coast to the finish.

About the Coast FIRE Calculator

Define yearly expenses today \(E\) and a withdrawal multiple \(M\) (often \(M\approx 25\)). Your independence target in today’s dollars is \(FI=E\cdot M\). Let nominal return be \(r\) and inflation be \(i\). The real return is

$$r_{\text{real}}=\frac{1+r}{1+i}-1.$$

If you plan to make no further contributions, and there are \(Y\) years until retirement, the present amount needed to coast is

$$P_0=\frac{FI}{(1+r_{\text{real}})^{Y}}.$$

If you will still contribute \(C\) per year for the next \(t_c\) years (until your coast age), work in nominal terms. First inflate the target:

$$FV_{\text{target}}=(E\cdot M)\,(1+i)^{Y}.$$ $$FV_{\text{contrib}}=C\cdot\frac{(1+r)^{t_c}-1}{r}\cdot(1+r)^{Y-t_c}.$$ $$P_0=\frac{FV_{\text{target}}-FV_{\text{contrib}}}{(1+r)^{Y}}.$$

Use MathJax to display these formulas responsively and math.js for precise calculations, while keeping the same equations visible to users.

How to Use this Coast FIRE Calculator

  1. Enter annual expenses \(E\) and choose a withdrawal multiple \(M\) (e.g., \(25\)).
  2. Set years to retirement \(Y\), expected nominal return \(r\), and inflation \(i\).
  3. If you’ll keep contributing for \(t_c\) years, enter yearly contribution \(C\); otherwise leave \(C=0\).
  4. Compute \(P_0\) via the real-return formula (no contributions) or the nominal formulas (with contributions).
  5. Compare \(P_0\) to your current portfolio; if current ≥ \(P_0\), you’re at (or past) Coast FIRE.

Examples (using the same formulas)

Example 1 — No further contributions:
\(E=\$40{,}000,\ M=25 \Rightarrow FI=\$1{,}000{,}000.\) Years \(Y=25,\ r=7\%,\ i=2.5\%\).
\(r_{\text{real}}=\frac{1.07}{1.025}-1\approx 0.0439.\) Then $$P_0=\frac{1{,}000{,}000}{(1.0439)^{25}}\approx \$341{,}000.$$

Example 2 — Contribute for 10 more years:
Same \(E, M, Y, r, i\) and \(C=\$12{,}000,\ t_c=10\).
\(FV_{\text{target}}=1{,}000{,}000\,(1.025)^{25}\approx \$1{,}850{,}000.\)
\(FV_{\text{contrib}}=12{,}000\cdot\frac{(1.07)^{10}-1}{0.07}\cdot(1.07)^{15}\approx \$458{,}000.\)
Then $$P_0=\frac{1{,}850{,}000-458{,}000}{(1.07)^{25}}\approx \$256{,}500.$$

FAQs

Q1: What multiple should I use—25×, 30×, or something else?
Choose a multiple tied to your safe withdrawal rate (e.g., \(M=1/\text{SWR}\)). Higher multiples add safety for long retirements.

Q2: Should I input nominal or real returns?
If using the simple coast formula, use real return \(r_{\text{real}}\). If modeling contributions and inflation explicitly, use nominal \(r\) and \(i\).

Q3: How do taxes and fees affect the result?
Reduce \(r\) for after-fee returns and increase \(E\) for after-tax spending needs to keep assumptions realistic.

Q4: Can I include Social Security or pensions?
Yes—subtract expected guaranteed income from \(E\) before computing \(FI=E\cdot M\).

Q5: What if markets underperform?
Recompute annually. If returns lag, keep contributing longer or raise \(M\) to maintain a conservative plan.

More Finance & Business Calculators
Bridge Loan Calculator
Car Loan Refinance Calculator
Car Sales Tax Calculator
Cubic Yards Calculator
Diminished Value Calculator
Fers Retirement Calculator
Fill Dirt Calculator
Grade Curve Calculator
Mortgage Recast Calculator
Pain And Suffering Calculator
Prorate Rent Calculator
Rv Loan Calculator