Coast FIRE

Coast FIRE is the point at which a person's existing retirement savings are large enough that, with no further contributions, projected compound growth would carry the balance to their retirement target by a traditional retirement age. Once past it, the saver can "coast": continue working to pay current bills while the portfolio matures on its own. The concept front-loads retirement saving into the early career years, when each dollar has the most decades to compound.

The Coast FIRE number is a discounting exercise: take your retirement target and shrink it backward by an assumed growth rate for each year between now and retirement. Formally, Coast number = target ÷ (1 + r)^n, where r is the assumed annual return and n the years remaining. Every input is soft — the target depends on future spending you're guessing at, and r is an assumption about decades of market behavior. Small changes in r move the answer enormously over 30-plus years, which is why careful planners run the math at several return assumptions (and in inflation-adjusted terms) rather than trusting one rosy number.

The strategic appeal is sequencing. A dollar invested at 25 has roughly four decades to compound; a dollar invested at 55 has one. By concentrating sacrifice in the years when compounding is most powerful, Coast FIRE buys back flexibility in mid-life — the years when careers plateau, kids are expensive, and burnout peaks. The risks mirror the appeal: coasting means trusting projections for a very long time with no contribution cushion, and a decade of poor returns, higher-than-expected spending, or an early forced retirement can leave a coaster short with fewer years to correct. Most practitioners treat Coast status as permission to downshift, not a reason to stop monitoring the plan.

Pick a retirement age and target amount, choose a conservative assumed return, and discount the target back to today. If your current retirement balance meets or exceeds that discounted figure, you've reached Coast FIRE.

A hypothetical example: Leo is 30, wants the option to retire at 65, and estimates he'll need about $2 million. At an assumed 7% average annual return (illustrative only — not a prediction), $200,000 today would grow for 35 years to roughly 200,000 × 1.07³⁵ ≈ $2.1 million. Leo has $210,000 saved, so under those assumptions he's past his Coast FIRE point: even contributing nothing more, his existing savings project to cover retirement. Rerun at a more cautious 5%, though, the same $210,000 grows to only about $1.16 million — which is exactly why the assumption, not the milestone, deserves the scrutiny.

Pros

• Converts retirement from a lifelong obligation into a problem largely solved early, buying decades of career flexibility.
• Uses compound growth at maximum strength — early dollars do the work of many later ones.
• Downshifting to work you like (at lower pay) becomes financially rational instead of reckless.

Cons

• The milestone rests entirely on long-range assumptions; an optimistic return estimate can declare victory that the markets never deliver.
• Coasting removes the contribution habit and the cushion it provides — falling behind later is harder to fix with fewer compounding years left.
• Inflation and lifestyle changes can quietly raise the real target while the portfolio is left alone.
• It answers the retirement question only; emergencies, home purchases, and college still need their own funding from current income.