TL;DR
How much do you need invested today so that, with zero new contributions, you land near your FIRE number by retirement? That backwards number is your coast number. Hit it, and you can keep working for rent and groceries if you want, skip the aggressive retirement saving, and let time do the heavy lift.
Say you want $1.5 million invested by age 60 (roughly $60k of yearly spending at a 4% withdrawal rate). You are 30 today. Markets return something like 7% a year on average, which is a planning assumption, not a promise.
Work the growth backwards and you get the coast number. Miss it, and you are not failing. You just still have a gap to close before coasting is honest.
Most people hear FIRE and picture quitting next Tuesday. Coast FIRE is quieter than that. You still work. You still earn. You just stop needing your paycheck to fund the future, because the nest egg you already built can finish the job through compound growth.
Play with it
Numbers on a page stay abstract. Drag these around until the story clicks. Portfolio growing with no fresh deposits versus the flat FIRE target you are aiming for.
If the curve finishes under the target, you are not coasting yet. Raise what you have invested, give yourself more years, or lower the lifestyle you plan to fund. The chart will tell you which lever actually moves the needle.
How the math stays simple
You do not need a PhD spreadsheet. Coast FIRE is discounting your future FIRE number back to today:
Coast number = FIRE number ÷ (1 + expected return)^years left
FIRE number itself is usually annual spending ÷ safe withdrawal rate. Plenty of people use 4%. Some use 3.5% if they want more cushion. Pick a rate you can live with, then stick with it long enough to compare apples to apples.
A few honest caveats. Returns are not smooth. Inflation eats purchasing power. Life gets expensive in uneven ways. The formula is a compass, not a contract with the market.
Who this is actually for
Coast FIRE tends to fit people who:
- Already saved hard for a stretch and want to know if the pressure can ease
- Are fine working longer if the work is lighter or more meaningful
- Care more about optionality than a hard quit date
- Want a milestone that is reachable before "never have to work again"
It is a weaker fit if your goal is to stop working as soon as possible, or if your portfolio is still small and the coast number is years of aggressive saving away. In those cases classic FIRE math (how much to save each month to hit FI on a date) is usually more useful day to day.
Coast vs regular FIRE
Regular FIRE asks: when can I stop needing a paycheck entirely?
Coast FIRE asks: when can I stop feeding the portfolio, because growth can finish the race?
Both use the same end target. Coast just separates "have enough later" from "live off it now." A lot of people hit coast years before they hit full FI. That middle stretch is where life can open up: career changes, travel, kids, a business, without pretending the retirement account still needs every spare dollar.
A practical way to use it
- Pick a retirement age and a yearly spend you believe.
- Convert that spend into a FIRE number (spend ÷ withdrawal rate).
- Discount it back to a coast number with a return assumption you are willing to defend.
- Compare to what you have invested today.
- If there is a gap, decide whether to close it with more saving, more time, or a smaller future lifestyle.
Then check it once or twice a year. Not every Friday. Coast is a milestone, not a dashboard addiction.
If you want the fuller calculator with ages, withdrawal rate, and a cleaner projection, use the Coast FIRE calculator on Violetly. Same math as the widget above, just more room to dig.
Why I care about this milestone
When I talk about financial independence, coast shows up a lot. It is one of the first moments the plan starts to feel real: the future is no longer only "save harder." It becomes "protect what is already working."
That is also why Violetly tracks past decisions, present balances, and future projections together. A coast number without context is trivia. A coast number sitting next to your actual portfolio and the life you said you wanted is a decision.
If this helped the idea click, good. Change the inputs. Sit with the gap or the surplus. Then go live your Tuesday.