FIRE glossary
Coast FIRE
The point at which your existing savings, left to grow untouched, will reach your FIRE number by your target retirement age — so you can stop investing new money and still get there.
How Ember computes it
Ember's coastFireDate function compounds your current investable pot forward at your real (post-inflation) return assumption, with no further contributions, and finds the earliest current age at which that projection alone already reaches your required pot — SWR or drawdown-to-zero, whichever basis you've set — by your target retirement age. It's a single forward-projection question: if you stopped adding money today, would growth alone finish the job in time?
Coast now, or coast later
If today's pot already clears the bar on its own, you're already "currently coasting" — the engine reports that directly, no further search needed. If not, it walks forward year by year using your actual planned contribution schedule to find the first future age at which stopping contributions would still leave enough time for growth alone to reach the target. That future age, not today's, is your coast date.
What it doesn't capture
The calculation uses a single constant real-return assumption, not a range of possible outcomes — a Coast FIRE age computed this way is a point estimate, not a probability. Pairing it with a Monte Carlo simulation shows how sensitive that date actually is to the order in which real returns arrive, rather than the average return alone.
Why the target age matters
Coast FIRE is defined relative to a target retirement age, not an age in the abstract — push that target out and the required growth period lengthens, which can turn an unreachable coast age into a reachable one on exactly the same pot and contribution schedule. The two numbers move together, not independently, so widening the horizon is one of the simplest levers if a coast age looks out of reach today.
Worked example
A 35-year-old with $200,000 invested, at 5% real growth
Coast age
not reached by 55
Required pot at 55
US$1,000,000
Fixed illustrative inputs, not your data — for the exact maths behind your own numbers, use the free calculator or build a plan. Educational modelling, not financial advice.
Across borders
The required pot you're coasting toward is grossed up for tax at your residency, so a planned move to a different tax residency before your target retirement age changes the bar you're aiming to clear — not just the number you'll eventually spend.
Common questions
What if I never reach Coast FIRE before retirement?
The coast age comes back as unreachable — it means your current pot plus contribution schedule doesn't clear the bar without continuing to contribute all the way to retirement.
Does Coast FIRE assume I stop earning entirely?
No — it assumes you stop investing new money into the portfolio, not that you stop working. Combining reduced-but-not-zero work income with a partially-funded pot is Barista FIRE, a related but distinct model.
Is a real or nominal return used?
Real (post-inflation) — see the real-vs-nominal-returns term for why that distinction matters over long horizons.
Related terms
See coast fire in your numbers
The free calculator gives a rough estimate; the full planner models your actual accounts, pensions, residency moves and taxes — with the maths behind every figure shown.