Coast FIRE is the point where you've invested enough that compound growth alone — with zero additional saving — carries you to your FIRE number by retirement. Enter your savings, target spending, and assumptions to see whether you've hit your coast number, all in today's dollars so the figures stay intuitive.
We convert your nominal return to a real (after-inflation) return so every number is in today's dollars: real return = (1 + return) ÷ (1 + inflation) − 1.
Your FIRE number is the nest egg that funds your spending under the safe-withdrawal rule: annual spending ÷ withdrawal rate (4% by default → 25× spending).
Your coast number is that FIRE number discounted back to today by your real return over the years until retirement — the amount you'd need invested NOW to coast.
Surplus or shortfall = current savings − coast number; a positive figure means you can stop saving and still reach your goal on growth alone.
Coast FIRE means you have enough invested today that, even if you never contribute another dollar, compound growth will reach your FIRE number by retirement. You still work to cover current expenses, but you no longer have to save for retirement.
How is the coast number calculated?
We take your FIRE number (annual spending ÷ withdrawal rate) and discount it back to today using your real, after-inflation return over the years left until retirement. That present value is the amount you'd need invested now to coast.
Why are the results in today's dollars?
Working in real (inflation-adjusted) dollars keeps every figure comparable to what money is worth today, so a $1.25M FIRE number means today's spending power — not an inflated future amount that's hard to gauge.