Coast FIRE Calculator
Plan Your Path to Financial Independence

What Coast FIRE actually means

Coast FIRE is the moment your invested savings are large enough that, even if you never contribute another dollar, compound growth alone will carry the balance to your full retirement target by the age you plan to stop working. You haven't retired - you still cover your day-to-day expenses with income - but you no longer have to save for retirement. The heavy lifting is done, and time in the market does the rest.

That distinction is what makes Coast FIRE such a useful milestone. Traditional FIRE asks how much you need to quit work entirely. Coast FIRE asks a gentler, earlier question: how much do you need today so you can stop adding to your retirement accounts and simply coast? For most people that number arrives years - sometimes a decade - before full financial independence, which is why it is such a motivating checkpoint.

The Coast FIRE formula, with a worked example

The calculation has two steps. First, find your full FIRE number: annual retirement spending divided by your safe withdrawal rate. At a 4% withdrawal rate, $40,000 of yearly spending needs a $1,000,000 nest egg. Second, discount that figure back to today using your expected real return and the number of years until retirement: Coast FIRE number = FIRE number divided by (1 + return) raised to the power of the years remaining.

Worked example: a 30-year-old who wants to retire at 60 needs $40,000 a year, giving a $1,000,000 FIRE number. With a 5% real return over 30 years, the growth factor is 1.05^30, or about 4.32. Dividing $1,000,000 by 4.32 gives a Coast FIRE number of roughly $231,000. If this person already has $231,000 invested, they can stop contributing today and still reach $1,000,000 by age 60 - that is Coast FIRE.

The calculator above runs this math instantly and plots it: the rising line is your projected balance, the target line is what you need, and the point where they meet is the year you reach Coast FIRE.

How to use this calculator

Enter your current age, the age you plan to retire, the amount you already have invested, and your expected annual spending in retirement. Then set your assumptions - expected growth rate, inflation, and safe withdrawal rate - or leave the sensible defaults in place. The result updates to show your Coast FIRE number, whether you have already reached it, and the year your portfolio is projected to coast to your goal.

Try adjusting one input at a time to see what moves the needle. Pushing your retirement age out by a few years, or trimming your expected spending, can lower your Coast FIRE number dramatically because compounding has more time to work.

Coast FIRE vs Barista, Lean, Fat, and traditional FIRE

Coast FIRE sits within a family of FIRE strategies that differ mainly in how much you need and how you get there. Traditional FIRE means saving enough - typically 25 times your annual spending - to live off withdrawals indefinitely. Lean FIRE targets a frugal lifestyle with a smaller number, while Fat FIRE aims for a generous one. Each is a different finish line for the same race.

Barista FIRE is the closest cousin to Coast FIRE: both let your investments compound untouched while income covers your expenses. The difference is that Barista FIRE specifically assumes part-time or lower-stress work - often kept for the health insurance or benefits - whereas Coast FIRE only requires that some income, from any source, covers your spending while you coast.

Choosing your return and withdrawal-rate assumptions

Your results are only as good as your assumptions, and the two that matter most are your expected return and your withdrawal rate. Historically the S&P 500 has returned roughly 7% per year after inflation, but a real return of 5% is a more conservative planning figure once fees and a diversified portfolio are accounted for. Lower the return assumption and your Coast FIRE number rises, because you are giving compounding less help.

The 4% withdrawal rate comes from the Trinity Study, which tested how much retirees could withdraw over a 30-year retirement without running out of money. It is a useful default, not a guarantee - some planners prefer 3.5% for longer retirements or extra caution. Treat these inputs as dials, not facts: run the calculator with a range of values to see how sensitive your plan is.

Common mistakes to avoid

The most common error is mixing nominal and real numbers - using a 7% nominal return but forgetting that inflation will raise the cost of your future lifestyle. Either use a real, inflation-adjusted return throughout, or inflate your spending target to match. The calculator handles this for you when you set an inflation rate.

Two other traps: assuming an optimistic return you would not bet your retirement on, and treating Coast FIRE as the end of planning. Reaching your Coast FIRE number means you can stop saving for retirement - it does not mean you can stop investing wisely, managing risk as you age, or revisiting the plan when your spending or timeline changes.