Practical money guide
FIRE models a portfolio large enough to support spending. Coast FIRE models a smaller portfolio that could grow to that target by retirement without further contributions. Living expenses before then still need funding.
At $40,000 of annual spending and an assumed 4% withdrawal rate, the target is $1,000,000 in today's purchasing power. The 4% input is an assumption for this example, not a promise that withdrawals will be safe. Taxes, fees, other income, and the order of market returns are outside this simplified projection.
Consider age 35 and retirement at 65. With 7% nominal annual return compounded monthly and 2% annual inflation, the nominal retirement target is about $1.81 million. Dividing it by the modeled thirty-year growth factor gives a Coast FIRE threshold today of about $223,170. Monthly compounding matters; an annual-compounding calculator will give a different number.
A $120,000 starting portfolio is below that threshold. With the default $1,200 monthly contribution, this model reaches its moving coast threshold around age 45. It then stops contributions in the coast projection. You would still need income or separate assets for living expenses until retirement. Change monthly investment to zero to test the existing portfolio alone.
Lower the return, raise retirement spending, and try an earlier retirement age one at a time. Then combine a plausible downside case. These deterministic calculations cannot reproduce market volatility or guarantee future purchasing power. Use the FIRE calculator to examine continued contributions and the investment calculator to inspect nominal and inflation-adjusted growth.
Live model
Enter your assumptions to see an estimate. Use source view to inspect or change the calculation. Your inputs stay in this browser.
template: coast_fire current_age = 35 retirement_age = 65 current_portfolio = 120000 in usd monthly_investment = 1200 in usd annual_spending = 40000 in usd return_rate = 7% inflation_rate = 2% withdrawal_rate = 4% compounds_per_year = 12
Inputs
Method
retirement_target = annual_spending / withdrawal_ratereal_return = (1 + nominal_return) / (1 + inflation) - 1coast_number_today = retirement_target × (1 + inflation)^years / (1 + nominal_return / compounds_per_year)^(years × compounds_per_year)The inputs and source use the same model. Open it in Continuum for a document you can keep and revisit.
Worked example
Whether $120,000 is enough to coast depends on the real return over three decades. A modest assumption change can move the checkpoint by years.
Questions
No. It describes a modeled retirement-saving milestone. Current expenses still need a funding source until the retirement portfolio is used.
Compare inflation treatment, compounding frequency, contribution timing, retirement age, and withdrawal assumptions. Matching the inputs is necessary before comparing outputs.
Set monthly investment to zero. The result then shows whether the existing portfolio can reach the target under the other assumptions. An unreachable result is useful information, not a forecast of failure.
Keep the reasoning
The full template opens as a local Continuum document. Edit every assumption, explore the result breakdown, and keep the source.
Open coast fire vs fire: two different milestones