Coast FIRE, without the shortcuts
Coast FIRE asks whether the money already invested could grow to a retirement target without further contributions. It is a planning milestone—not permission to ignore uncertainty.
What “coasting” actually means
Traditional financial independence asks whether a portfolio can support spending today. Coast FIRE asks an earlier question: if contributions stopped now, could the existing portfolio compound to the amount needed at a chosen retirement age? Before retirement, earned income still has to cover current living costs. The milestone changes the role of saving; it does not eliminate the need to work.
The calculation has two stages. First, annual retirement spending is divided by a withdrawal rate to estimate a portfolio target at retirement. Second, that future target is discounted back to today using an assumed real return—the investment return after inflation.
Suppose someone wants $60,000 a year from a portfolio at 65 and uses a 4% withdrawal rate. The retirement target is $1.5 million in today’s dollars. With 30 years and a 5% real return, the amount needed today is about $347,000. A current portfolio above that figure meets the calculator’s mathematical definition of coasting under those assumptions.
How to use the result
Start with spending, not a round portfolio goal. Estimate the annual amount the portfolio—not Social Security, a pension, or part-time work—must fund. Keep the spending and return assumptions in the same kind of dollars: this calculator uses today’s purchasing power, so the return should be after inflation.
- Enter current age and the age when withdrawals are expected to begin.
- Enter invested assets that are genuinely intended for retirement. Do not include emergency cash or home equity unless the plan explicitly depends on them.
- Choose retirement spending and a withdrawal rate together. A lower rate requires a larger target.
- Test the result again with a lower real return, higher spending, and an earlier retirement date.
Stress-test before changing contributions
A single expected return hides the order in which gains and losses arrive. A portfolio can average the assumed return and still finish below the target if poor returns occur late, fees run high, or the asset mix becomes more conservative. Run at least three scenarios: a base case, a cautious case with returns one to two percentage points lower, and a spending case 10% to 20% higher.
Also separate “mathematically on track” from “personally safe.” Continued contributions can fund flexibility, early retirement, healthcare, family support, or a margin against bad markets. Reaching a coast number may support reducing contributions; it does not automatically make that choice prudent.
What the number leaves out
The tool does not model taxes, account types, investment fees, Social Security, pensions, required minimum distributions, healthcare, longevity, or changing spending. It assumes one steady real return. Those omissions make it useful for orientation and scenario comparison, not as a retirement plan.
Use the coast number as a checkpoint. Confirm the result in a full retirement projection before reducing savings, changing jobs, or relying on a specific retirement date.