Coast FIRE Planner

What Coast FIRE means

Coast FIRE is the point at which your invested savings are large enough to compound toward your full retirement target on their own, even if you stop adding new money. After reaching it, contributions become optional: your existing balance compounds toward the target while your income only needs to cover day-to-day spending. This planner projects your balance year by year so you can see when, and whether, that point arrives under your assumptions.

How the projection works

The planner compounds your current investments at the growth rate you set, layers in any ongoing contributions and a retirement event if you add one, and adjusts for inflation when you switch to the today’s-money view. The net worth line shows the long arc; the cashflow and money-flow views show each year in detail. Because the maths is compound, an earlier start or a slightly higher assumed return moves the coast point by years rather than months.

How to use it

Start from a template close to your situation, then set your current investments, income, expenses and assumptions. Add a retirement event on the timeline to mark when contributions could stop. Read the projected net worth, then test a cautious and an optimistic growth rate to see the range of outcomes rather than a single figure. Save scenarios to compare contributing more now against coasting sooner.

Assumptions and limits

The projection holds your assumptions steady unless a life event changes them, and uses a single optional flat tax rate on income rather than any country-specific tax rules. Real markets vary and returns are uncertain, so treat the coast point as an illustration to revisit, not a guarantee. For personal decisions, consult a qualified professional.

Coast FIRE versus full FIRE

Full FIRE means your portfolio could cover your living costs indefinitely, often estimated as roughly 25 times your annual spending. Coast FIRE is an earlier milestone: the portfolio is not large enough to live on yet, but it is large enough that, left untouched, compound growth alone could carry it to a full-FIRE balance by your target age. The difference between the two is mostly time, and this planner shows the running balance so you can see how far along that path your current assets sit.

What the result shows

The headline figure is the projected net worth at your target age under the inputs you entered. The peak and low markers show the range across the projection, and the funding indicator flags whether the plan stays solvent to the end. Switching to the today’s-money view divides each year by compounded inflation, so a large nominal figure is shown in terms of what it could buy now. Reading both views together gives a fuller picture than either alone.

A worked example

Consider a 30-year-old with 120,000 already invested, growing at an assumed 7% a year, who adds nothing further. Over 30 years that single balance compounds toward roughly 900,000 in nominal terms before any new contributions, which is the essence of coasting. Add ongoing income and expenses and the planner layers your yearly surplus on top. At an assumed 4% the same starting balance reaches a much lower figure, which is why testing a range of rates is more informative than reading one number.

Privacy

Every figure is calculated in your browser and saved to local storage on your own device. There is no account and no server round-trip, and a shared plan is encoded into the link itself.