Coast FIRE Calculator

Frequently asked questions

What is Coast FIRE?

Coast FIRE is the point where the money you have already invested, left completely alone, will grow through compounding into a full retirement by a traditional retirement age, with no further contributions required. Reaching it does not mean you stop working; it means you stop being required to save, so a lower-paying, lower-stress, or part-time role becomes financially possible without pushing your retirement date back.

How is this different from a regular FIRE calculator?

A FIRE calculator asks how much you need invested to retire and live off withdrawals starting now, or soon. A Coast FIRE calculator asks a narrower question: how much do you need invested today so that growth alone, with zero further contributions, reaches your full FIRE number by a later retirement age. The Coast number is always smaller than the full FIRE number, because it has years of compounding still to do the rest of the work.

Why does this calculator ask about Social Security or a pension?

Because leaving it out overstates what you need. If you expect $20,000 a year from Social Security or a pension starting at retirement, your portfolio only has to cover the remaining spending, not all of it. Most Coast FIRE calculators, including the well-known ones, skip this entirely and tell you to do the subtraction yourself. This one does it for you, which produces a genuinely smaller, more accurate Coast number for anyone who has a pension or a reasonable Social Security estimate. If you would rather build in extra margin, set this to $0 and treat your future benefit as a bonus.

What about my mortgage?

It isn't modeled as a separate line, on purpose, since payoff dates and remaining balances vary too much to default sensibly. The clean way to handle it: put your annual spending in as the number you expect to spend once the mortgage is gone, then check the answer changes appropriately if it is paid off partway through the horizon by running the calculator twice with two different spending figures, once for now and once after payoff, and reading the more conservative of the two.

Is a 4% withdrawal rate still safe for an early retirement?

The 4% figure comes from William Bengen's 1994 research and the later Trinity Study, both built around a 30-year retirement horizon. Retiring in your 30s or 40s can mean a 50-to-60-year horizon, which most planners since have argued needs a lower, more conservative rate, often 3.25% to 3.5%, to hold up. This calculator defaults to 4% because it is the number everyone recognizes, but the safe withdrawal rate field is yours to lower for a longer runway.

What return rate should I actually use?

The calculator asks for a nominal investment return and an inflation rate separately, then subtracts both inflation and your entered fee drag to get a real return, rather than asking you to guess a single blended number. A common starting point is 10% nominal for a stock-heavy portfolio (the long-run US market average before inflation) and 3% inflation, for a real return before fees of roughly 7%. Bonds, a more conservative allocation, or the years right before retirement typically justify a lower figure.

What's the difference between Coast FIRE and Barista FIRE?

Coast FIRE lets your investments stop needing contributions while you still cover your own living costs some other way, whether that is your current job, a new one, or something part-time. Barista FIRE specifically means covering costs through part-time or lower-stress work chosen for its benefits or flexibility, the term comes from taking a job like a barista role partly for the health insurance. Every Barista FIRE plan rests on a Coast FIRE number underneath it; this calculator answers the number both strategies need.

What does the Monte Carlo section add that the calculator above does not already show?

The main calculator answers 'what does the plan imply if the same average return shows up every year.' Real returns don't work that way, some years are down 20%, some are up 30%, and the order they happen in matters. The Monte Carlo section runs 500 different random sequences of annual returns around your same assumptions and reports how many of them actually reach the coast number, plus the spread between a lucky run and an unlucky one. A plan can look fine on the average-return line and still fail in a meaningful share of the 500 runs; that gap is the entire reason to check both.