FAQ
Straight answers on how the calculator works, what it assumes, and where those assumptions come from.
Coast FI is the point at which you have enough invested that, left alone with no further contributions, compound growth alone would carry it to your full retirement number by your target retirement age. Once you hit Coast FI, you technically don't need to save any more for retirement — though most people keep working and contributing to retire sooner or with more cushion, which is what the accumulation phase of this calculator models.
FIRE is a movement centered on saving and investing aggressively so your investment portfolio can cover your living expenses well before traditional retirement age, giving you the option to stop working for pay. Coast FI, Lean FIRE, and Fat FIRE are all variations on how much is saved and how the withdrawal phase is structured.
A typical 4% rule calculator only answers one question: does a fixed withdrawal rate survive a fixed number of years. The Long Coast runs both halves of your financial life together — the years you're still contributing, and every year of spending down after that — as one continuous projection, and shows the classic 4% rule figure alongside your own numbers for comparison rather than as the only benchmark.
The 4% rule, based on historical U.S. market research (the Trinity Study), is the most commonly cited starting point for a 30-year retirement. The common FIRE shorthand of saving "25x your annual expenses" is the same rule expressed as a multiple instead of a percentage (1 divided by 4% equals 25). Withdrawal rates below your expected real rate of return tend to let a portfolio keep growing even while you spend from it; rates above your return draw the balance down over time. Many early retirees planning for a much longer than 30-year horizon target something closer to 3-3.5% instead, which is where the stricter "30x" or "33x expenses" targets come from.
A real return is your investment return after subtracting inflation. Using real returns throughout means every dollar figure in the calculator — your balance, your spending, your results — is already expressed in today's purchasing power, so you don't need to separately guess an inflation rate or inflate your future spending number by hand.
Long-run U.S. stock market real returns have historically averaged somewhere around 6.5-7% annually, though a diversified portfolio with bonds typically runs a bit lower. Many conservative planners use 5-6% to build in a margin of safety. This calculator defaults to 7% but you can change it instantly to see how sensitive your outcome is to that assumption.
No. This is a deterministic projection that assumes the same real return every single year, which real markets never deliver. In reality, a bad string of returns in the first several years of retirement (sequence-of-returns risk) can deplete a portfolio much faster than the same average return spread evenly over time. This tool is meant for building intuition about compounding and withdrawal rates, not as a substitute for Monte Carlo or historical cycle testing.
Not currently. The calculator models a single portfolio being contributed to and then drawn down, in real dollars, without modeling taxes, Social Security benefits, pensions, or part-time/Barista FIRE income. Treat the spending figure as your after-tax, all-in annual number and adjust it to approximate your own situation.
No. All of the math runs locally in your browser using JavaScript. Nothing you type is transmitted to a server or stored in a database. The only thing that changes is the page's own URL, which encodes your inputs so you can copy and share a link to a specific scenario. See the privacy page for more detail.
No. The Long Coast is an educational tool for exploring how contributions, returns, and withdrawal rates interact over time. It is not financial, tax, or legal advice. Speak with a qualified financial advisor before making decisions about your retirement savings or withdrawal strategy.