Quick answer
Coast FIRE is the moment your invested portfolio is large enough that compound growth alone — with zero additional contributions — will reach your full FIRE number by traditional retirement age. You still need to cover daily expenses, but you can stop investing. The formula is simply your FIRE number discounted backward at your assumed real return.
What Coast FIRE actually means
The point where contributions become optional — not the point where work becomes optional.
Coast FIRE describes a stage on the path to financial independence, not a destination. You reach Coast FIRE when your portfolio is large enough that, left untouched, compound growth alone will carry it to your full FIRE number by the age you plan to fully retire. You still have to work — but only to cover current living expenses. You no longer need to save.
Two ideas matter here. First, Coast FIRE is a milestone, not an exit. The money keeps growing in the background while you keep earning. Second, it is the earliest meaningful checkpoint on the FIRE path for most people — typically reached a decade or more before full FI — which makes it the variant worth tracking even if your long-term target is Lean or Fat FIRE.
How to calculate your Coast FIRE number
Take your future FIRE number and discount it back to today at your real return.
The Coast FIRE number is the present value of your future FIRE number, discounted at your expected real (inflation-adjusted) annual return.
r = expected real return; n = years until target retirement age.
A worked example. Suppose your expected retirement spending is $50,000 per year, so your FIRE number is $1,250,000. You are 30, want to retire at 60 (so n = 30), and assume a 5% real return. The Coast FIRE number is:
Reach roughly $289,000 invested by age 30 and you have hit Coast FIRE. From that day on, you only need to earn enough to cover current expenses; compound growth does the rest of the heavy lifting.
The free Coast FIRE Calculator runs this math instantly for any combination of current age, target age, expenses, and return assumption.
How starting age and target age move the number
The earlier you start and the later you retire, the smaller the Coast FIRE number — by a lot.
Two levers dominate the Coast FIRE math: how long compound growth has to work, and what real return you assume. The table below shows the Coast FIRE number for a $1,250,000 target ($50,000 spending × 25) at a 5% real return.
| Current age | Target retirement age | Years to grow | Coast FIRE number |
|---|---|---|---|
| 25 | 60 | 35 | ~$226,500 |
| 30 | 60 | 30 | ~$289,200 |
| 35 | 60 | 25 | ~$369,000 |
| 40 | 60 | 20 | ~$471,100 |
| 40 | 65 | 25 | ~$369,000 |
| 45 | 65 | 20 | ~$471,100 |
The same FIRE target — $1.25M — becomes a $226K problem at 25 and a $471K problem at 40. The lesson is not new but worth saying clearly: time in the market is the single most valuable currency in the FIRE math, more than salary or savings rate.
Coast FIRE vs Barista FIRE — easy to confuse
Both let you stop saving. Only one assumes you keep working full time.
The two milestones sound similar and are routinely mixed up. They are not the same.
- Coast FIRE assumes you continue to work full time at your current income. You stop investing, but your job still funds your full lifestyle. The portfolio compounds untouched in the background until your target retirement age.
- Barista FIRE assumes you switch to part-time or lower-paying work that no longer covers your full expenses. The portfolio supplies the gap through small, planned withdrawals — long before traditional retirement.
The practical difference is touch versus no-touch. Coast FIRE is purely a savings pause; Barista FIRE is the start of partial withdrawals, which means sequence-of-returns risk begins to bite years earlier. Read more on that in the sequence of returns risk article.
What Coast FIRE assumes — and where reality bites
The formula is clean. The assumptions inside it deserve a hard look.
Coast FIRE is one equation with three assumptions. Each one can break the plan if you set it carelessly.
- Real return. The 5% real used above is the long-run US equity average, not a guarantee. A decade of 2–3% real returns — entirely possible — turns a 30-year Coast FIRE into a 35-year one. Build in margin: assume 4–4.5% real for 20-to-30-year horizons, not 7%.
- Stable expenses. The math assumes your target spending in retirement equals what you plan today, adjusted for inflation. Lifestyle creep, kids, healthcare, or a long-distance move can invalidate the original FIRE number, which retro-invalidates the Coast number derived from it.
- You actually stop contributing. The math only works if the portfolio is left alone. People who reach Coast FIRE and immediately rebalance into “low volatility” assets at the wrong moment, or who borrow against the portfolio, break the assumption.
Sanity check: re-run the Coast FIRE calculation every 2–3 years using your latest expense data and a sober real-return assumption. If the new Coast number is higher than what you have invested, the plan has drifted and contributions need to resume.
A Coast FIRE checklist
What to track once you hit the number and want it to keep working.
- Calculate your FIRE number first using the 25× rule. Coast FIRE is meaningless without a target.
- Pick a real return you would defend in front of a skeptical financial planner. 4–5% is defensible in 2026; 7% is not.
- Choose a target retirement age you actually want — not the one that produces a flattering Coast number.
- Keep the portfolio in a globally diversified, low-cost index allocation. Stock-heavy is appropriate while you are still working and the portfolio is left untouched.
- Re-check annually. Bump assumptions if inflation runs hot or returns disappoint.
Common questions about Coast FIRE
Three things people ask once the concept clicks.
Is Coast FIRE the same as being financially independent? No. You are not FI — you still have to work to pay current expenses. You have only crossed the line where you no longer need to save.
Can I “un-Coast” if the market drops 30%? Yes, and most plans do at some point. A 30% drawdown two years after hitting Coast FIRE moves the line back; resuming contributions for a stretch fixes it. The framework is not fragile if you remain willing to adjust.
Does Coast FIRE work with a non-USD currency? Yes — the formula is currency-neutral. Use your local annual expenses, your local real return (developed markets all converge near 4–6% real over decades), and the same equation.