Coast FIRE Calculator

Coast FIRE is the point where you have enough invested that, without adding another dollar, compound growth alone will reach your full retirement number by the time you retire. Once you hit it you can "coast" - stop saving for retirement and only earn enough to cover today’s expenses - and still arrive at a fully funded retirement. It is the most reachable milestone on the FIRE spectrum, especially for people who start young.

First find your FIRE number - annual retirement spending divided by your safe withdrawal rate (spending times 25 at the classic 4% rule). Then discount that number back to today using your expected real (after-inflation) return over the years until retirement. That discounted figure is your Coast FIRE number: the amount that, left alone, compounds up to the FIRE number. This calculator does both steps and also finds the age you reach it if you keep contributing.

Full FIRE means your portfolio covers all your expenses and you never have to work again. Barista FIRE means you have enough that a part-time job (often for health insurance) covers the gap while your investments finish growing. Coast FIRE is earlier still: your retirement is already secured by compounding, so you only need to earn your current living costs - you are done saving, but not done working.

Mathematically, yes - if your assumptions hold, the balance grows to your target on its own. In practice, most people keep a cushion because returns are lumpy and life changes. Hitting Coast FIRE is best treated as freedom to ease off: switch to a lower-paying job you enjoy, take a sabbatical, or redirect savings to nearer-term goals, rather than stopping cold and hoping the market cooperates.

Use a real (after-inflation) return, since your future expenses are in today’s dollars. Historically a diversified stock portfolio has returned around 10% nominal and roughly 7% after inflation. This calculator lets you enter nominal return and inflation separately and works in the gap between them. Being conservative - assuming a lower real return - pushes your Coast FIRE number up, which is the safer error to make.

Yes - that is the whole reason this calculator asks for inflation separately. It converts your nominal return into a real return and keeps every figure in today’s dollars, so the FIRE number you see is what you would need in purchasing power now, not an inflated future number that looks scarier than it is. Ignoring inflation is the most common way Coast FIRE math goes wrong.

The 4% rule says you can withdraw 4% of your portfolio in year one and adjust for inflation each year with a low chance of running out over 30 years - so your FIRE number is your annual spending times 25. Longer retirements or caution argue for 3.5% or 3.25% (a bigger number times 28-31). This calculator lets you set the rate; a lower rate raises your target.

It is often the most realistic FIRE variant precisely because time does the heavy lifting. A modest sum invested at 30 has 35 years to compound, so the Coast FIRE number can be a fraction of the full FIRE target. The example on this page shows a 30-year-old with $50,000 and $1,000 a month reaching Coast FIRE in their late 30s - after which the retirement is essentially on autopilot.

A poor stretch of returns can push your real balance below the coast line, meaning you would need to resume saving to get back on track. That sequence risk is why the sensible move is to build a margin of safety - keep coasting-level contributions for a while after you technically hit the number, or assume a conservative return - rather than stopping the instant the calculator says you are there.

If you can, continuing to invest simply moves you from Coast FIRE toward Barista or full FIRE - an earlier or richer retirement. The value of Coast FIRE is optionality: it tells you that you have already won the retirement game, so any further saving is buying an earlier finish or a bigger cushion, not avoiding disaster. Many people use that freedom to take more career risk.