Coast FIRE Calculator

Frequently asked questions

What is Coast FIRE?

Coast FIRE represents the moment when the money you've already invested, left completely alone, will grow through compounding into a full traditional retirement, with no further contributions required. Reaching this milestone does not mean you stop working; it means your need to keep saving is eliminated, 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 begin taking withdrawals now, or soon, to fund your living expenses. A Coast FIRE calculator asks a narrower question: how large an investment needs to be today so that growth alone, with no further contributions, reaches your full FIRE number by your desired retirement age. The Coast number is always smaller than the full FIRE number, since there are still years of compounding left to finish the job.

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

Leaving it out gives you a number that's larger than needed. If you expect $20,000 a year from Social Security or a pension starting at retirement, your portfolio only has to cover the difference between that amount and your full spending, not all of it. Several well-known Coast FIRE calculators skip this entirely and leave you to do the subtraction yourself; this one does it for you, which produces a genuinely smaller, more accurate Coast number for anyone who expects a pension or a reasonable Social Security benefit. If you'd 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 are so variable that there's no sensible default. The clean way to handle it: enter your annual spending as the number you expect to spend once the mortgage is gone, then run the calculator twice with two different spending figures, once for now and once after payoff, and read 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 study and the later Trinity Study, both built around a 30-year retirement horizon. Most planners now argue that a longer horizon, at least 50 years for early retirees, needs a more conservative rate to hold up, often 3.25% to 3.5%. 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 (roughly the long-run US market average before inflation) and 3% inflation, for a real return after fees of around 7%. A larger bond 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's 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, so 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: in any given year you could see a loss of 20% or a gain of 30%, and the order those swings happen in matters. The Monte Carlo section runs 500 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.

Does this work as a Coast FIRE calculator for couples?

Switch "Household" to "Couple" and a second age field appears for your partner. Everything else, invested assets, contributions, spending, Social Security or pension, stays a single combined household figure, since that is how most couples actually track their money. The one number that changes behind the scenes is years to retirement: it counts down from the older partner's age, not the younger one's, because a joint portfolio only finishes compounding once both incomes are actually gone. Using the younger partner's age instead would understate what you actually need, handing you an over-optimistic Coast number.