Coast FIRE Calculator: $635,587 Coast Number vs $150,000 Saved at 30
Use this guide to understand the assumptions, inputs, results, and next steps behind the calculator.
Created by Luis Gonzalez · Last updated July 15, 2026
Coast FIRE is the point at which existing investments could grow to a retirement target without further contributions, assuming they earn a chosen return. Reaching that point does not mean you can stop working: you still need income to cover expenses until retirement, and the projection depends on investment and inflation assumptions.
This calculator estimates your Coast FIRE Number, FI Number, and Projected at Retirement. Enter your age, current savings, planned retirement age, annual retirement expenses, withdrawal rate, investment return, inflation, and life expectancy. For a broader introduction, read Coast FIRE explained and compare with the FIRE calculator or financial independence number calculator.
What the three results mean
The FI Number is the estimated portfolio needed at retirement to support the entered annual expenses using the selected withdrawal rate. The Coast FIRE Number is the smaller amount needed today, under the calculator's real-return assumption, to grow to that future FI target. Projected at Retirement grows your current savings at the nominal annual return, without subtracting contributions or withdrawals.
Those figures answer different questions. If projected savings at retirement are below the FI Number, there is a projected shortfall under the selected assumptions. If current savings are below the Coast FIRE Number, continued saving may be needed to reach Coast FIRE. Use the retirement number calculator and retirement goal calculator to examine other target-setting approaches.
Default example: follow the Coast FIRE calculation
The defaults are age 30, $150,000 in savings, retirement at 65, annual retirement expenses of $50,000, a 4% withdrawal rate, 7% annual return, and 2.5% inflation. There are 65 − 30 = 35 years to retirement. The calculator uses a real return of 7% − 2.5% = 4.5%.
First, it inflates the $50,000 annual expense assumption for 35 years: $50,000 × 1.025³⁵ ≈ $118,660. It then divides by the 4% withdrawal rate: $118,660 ÷ 0.04 ≈ $2,966,506, the displayed FI Number.
Next, the Coast FIRE Number discounts that future target by 35 years of real growth: $2,966,506 ÷ 1.045³⁵ ≈ $635,587. Current savings of $150,000 are $635,587 − $150,000 = $485,587 below that Coast FIRE Number.
The projected balance at retirement uses nominal growth: $150,000 × 1.07³⁵ ≈ $1,601,487. The calculator therefore displays a projected retirement balance below its $2,966,506 FI Number. These are model outputs, not guarantees; the projection assumes a steady annual return and does not model contributions, taxes, fees, or market volatility.
Formula and assumptions
Years to retirement = max(target retirement age − current age, 1)
Inflation-adjusted expenses = annual expenses × (1 + inflation rate) ^ years to retirement
FI Number = inflation-adjusted expenses ÷ withdrawal rate
Coast FIRE Number = FI Number ÷ (1 + real return) ^ years to retirement
The calculator defines real return as annual return minus inflation. This is a simplified approximation; an exact real return calculation would divide one plus the nominal return by one plus inflation, then subtract one. The result card uses the calculator's stated subtraction method, so keep that convention in mind when comparing projections.
The withdrawal rate is floored at 1% in the computation. A lower withdrawal rate raises the FI Number because the portfolio must be larger to support the same spending. The 4% rate is an assumption, not a universal safe rate. Retirement length, asset mix, fees, taxes, and the order of market returns can all affect whether a withdrawal plan lasts. See the safe withdrawal rate calculator and how to retire early: the math behind FIRE.
Test different assumptions
The table shows directional scenarios, not exact recalculated outputs. Each row changes one default input.
| Scenario | Changed input | Likely effect |
|---|---|---|
| Lower return | 5% instead of 7% | Raises the amount needed today and lowers projected savings at retirement |
| Higher inflation | 3.5% instead of 2.5% | Raises inflation-adjusted expenses and the FI target |
| Lower withdrawal rate | 3.5% instead of 4% | Raises the FI Number and Coast FIRE Number |
| Later retirement | Age 67 instead of 65 | Adds two years of modeled growth, but also changes the expense inflation period |
If you want to continue saving after reaching Coast FIRE, use a calculator that includes contributions, such as the retirement savings calculator. For a plan that includes part-time work, try Barista FIRE or Slow FIRE. A higher-spending target can be explored with Fat FIRE, while a leaner target can be tested with Lean FIRE.
Questions about Coast FIRE
Does reaching Coast FIRE mean I can quit my job?
No. It means your existing investments may grow to the modeled retirement target without additional contributions; it does not provide income for current expenses.
Why is the FI Number higher than the Coast FIRE Number?
The FI Number is the target portfolio at retirement. The Coast FIRE Number is the estimated present-day balance that could grow to that target over the remaining years.
Does the calculator include future contributions?
No. Projected at Retirement applies the annual return to current savings only. If you keep contributing, your actual balance could differ, but market returns could also be lower or uneven.
Should I use a 4% withdrawal rate or a lower one?
A lower rate produces a larger target and more room for withdrawals, but it may require saving longer or spending less. The calculator does not establish which rate is appropriate for your portfolio or retirement length.
Why does life expectancy not change the Coast FIRE Number?
The Coast FIRE Number formula uses years until the target retirement age. Life expectancy affects the growth chart's displayed age range, but it does not change the FI Number calculation in this model.
Can a steady 7% return be expected every year?
No. Returns vary, and a sequence of losses near retirement can affect a portfolio differently from the same average return earned steadily. The FIRE movement beginner's guide provides context for planning around these risks.
Next steps
Check the result using more than one return, inflation, and withdrawal-rate assumption. Then compare the target with projected income, taxes, and healthcare spending. If you plan to stop contributing, make sure your current income still covers expenses; if not, compare alternatives such as Sabbatical FIRE and Flamingo FIRE. For a detailed accumulation and withdrawal plan, use a retirement withdrawal calculator alongside this estimate.