Coast FIRE Calculator

Coast FIRE is the point where the money you have already invested will grow into your full retirement number on its own, without another dollar of contributions. This calculator finds that number. It capitalizes your planned retirement spending at your chosen withdrawal rate to get a full FI number, then discounts that number back to today at your expected real return over the years between now and your target retirement age. What comes back is the portfolio you would need right now to stop saving and still land on target.

The gap between the two figures is larger than most people expect. At a 5% real return over 25 years, a dollar invested today becomes $3.39, so a $1.5M FI number has a coast number of roughly $443,000 — under 7.4x annual spending, against 25x for full independence. Coast FIRE arrives at less than a third of the finish line, which is why it changes career decisions years before retirement does.

The page also answers the question people ask second: when. If you are still contributing, the projection finds the year your portfolio crosses the coast line and reports how much more you have to put in before that happens. And it publishes the coast number at every age up to retirement, because that column — walking from 7.4x spending at 35 to 25x at 60 — is the concept in one table.

It is for people whose question is not "can I retire" but "can I stop optimising for money".

• Anyone weighing a pay cut for a job they would rather do, who needs to know whether the savings rate they are giving up still matters.
• Mid-career savers with a large balance and a long runway, where compounding is already doing more work each year than contributions are.
• People considering a sabbatical, a startup, or a stretch of caregiving, who want to know what a few years of zero contributions actually cost.
• Parents deciding whether to front-load retirement saving now and coast through the expensive years rather than spreading contributions evenly.
• Anyone who has read that Coast FIRE arrives "about halfway" and wants the actual arithmetic for their own age, return assumption, and retirement date.

Every figure on this page follows from the four steps below. The calculation runs entirely in your browser; nothing is sent to a server or stored.

1. 1.Capitalize spending into a full FI number

   Your planned annual retirement spending is divided by your target safe withdrawal rate. This is the ordinary FIRE number — the balance that funds your spending indefinitely once you stop working. At 4% it is 25x spending; at 3.5% it is 28.6x.

   fi_number = annual_retirement_spending / withdrawal_rate

2. 2.Measure the runway

   The years between your current age and your target retirement age are the time your existing portfolio has to compound untouched. Ages are rounded to whole years. If your retirement age is not after your current age, the runway is zero and the coast number collapses onto the full FI number.

   years_to_retire = retirement_age - current_age

3. 3.Discount the FI number back to today

   The FI number is divided by the growth multiple your real return produces over that runway. This is the coast number: the balance that, left alone, arrives exactly at the FI number on your retirement date. Your surplus or shortfall is your current portfolio minus this figure, and the funded percentage is the ratio between them.

   growth_multiple = (1 + real_return) ^ years_to_retire
   coast_number = fi_number / growth_multiple
   coast_surplus = invested_portfolio - coast_number

4. 4.Project the crossing year, if you are still saving

   Contributions are added at the end of each year while the balance compounds, and the coast number is recomputed for the shrinking runway. The crossing is the first year the projected portfolio clears the coast number for that age. Crossings are bounded by your retirement horizon: if it does not happen before then, the tool reports that rather than extrapolating past your own deadline.

   coast_number_at_age_i = fi_number / (1 + r) ^ (years_to_retire - i)
   portfolio_i+1 = portfolio_i x (1 + r) + annual_contributions

Every figure is in today's dollars. There is no inflation field, and the reason is explained under assumptions below.

Current age

Your age today, rounded to a whole year. Together with the retirement age it sets the runway, which is the single largest lever on the coast number.

Target retirement age

The age by which you want the full FI number in place. Pushing it later shrinks the coast number sharply, because the growth multiple is exponential in the number of years. Must be later than your current age.

Annual retirement spending

Planned yearly spending in retirement in today's dollars, including taxes and health insurance. Divided by the withdrawal rate, it produces the full FI number that everything else is discounted from.

Invested portfolio

Market-invested balances only — brokerage, 401(k), IRA, HSA. This is the balance that compounds toward the FI number. Cash you do not intend to invest and home equity you do not intend to sell do not belong here, because neither compounds at the return you entered.

Annual contributions

What you still invest each year. Optional, and deliberately isolated: contributions set the date you reach the coast point, and never the coast number itself. The coast number is by definition what you would need if contributions stopped.

Withdrawal target

The safe withdrawal rate behind your FI number — presets at 3.5% and 4%, or a custom rate between 2% and 10%. A lower rate raises the FI number and the coast number in the same proportion.

Expected real return

Annual portfolio return after inflation. A stock-heavy portfolio has historically returned around 5% real over long horizons; 4% is a more cautious planning figure. This is the input the answer is most sensitive to, which is why the tool shows what one point less does to it.

The result panel leads with the coast number and the status; the rows beneath it show how that status was reached.

Coast FIRE number

The portfolio you would need invested today for compounding alone to reach your full FI number by your target retirement age. Also expressed as a multiple of annual spending, next to the multiple implied by your withdrawal rate.

Status

Already at your FI number: the portfolio covers full independence outright. Coasting: the portfolio is at or above the coast number. Nearly coasting: it is within 10% of it. Still climbing: further contributions are doing real work.

Surplus or shortfall

Your invested portfolio minus the coast number. A surplus is the buffer you hold above the coasting line; a shortfall is what you still have to accumulate before contributions become optional.

Coasting portfolio at retirement

Today's balance compounded to your retirement age with no further contributions, and the cushion that leaves against the FI number. This is the number that makes the coast claim concrete.

Coast crossing and full-FI crossing

The projected age and calendar year your contributions carry the portfolio past the coast number, and past the full FI number. Both are bounded by your retirement age; if neither happens before then, the tool says so rather than projecting past your deadline.

Coast FIRE number by age

The coast number at each age up to retirement, with the multiple of spending it represents and the portfolio your contributions are on track for at that age. The coast number rises every year, at exactly the rate your portfolio grows.

What moves the number

The coast number recomputed with one assumption changed at a time — a later or earlier retirement age, a 3.5% withdrawal rate, one point less real return — with the dollar swing each one produces.

These are the values behind the "Load example scenario" button, so every figure below is reproducible in the tool above.

1. Capitalising $60,000 of spending at 4% gives a full FI number of $1,500,000 — the ordinary 25x figure.
2. The runway is 60 - 35 = 25 years, and at a 5% real return the growth multiple over that runway is 1.05^25 = 3.38635494.
3. Dividing gives a coast number of $1,500,000 / 3.38635494 = $442,954.16. That is 7.38x annual spending, against 25x for full independence.
4. The $520,000 portfolio is $77,045.84 above that line, or 117.4% funded — the status reads Coasting.
5. Compounding $520,000 for 25 years with zero further contributions reaches $1,760,904.57 by 60, a cushion of $260,904.57 over the $1.5M target.
6. Keeping the $18,000 a year going instead clears $1.5M sixteen years out, at $1,560,929.64 — full financial independence at 51, nine years ahead of the retirement date.
7. The by-age table shows why the answer is not fragile: the coast number rises from $442,954.16 at 35 to $1,500,000 at 60, and the multiple of spending walks cleanly from 7.38x to 25x.

The instructive part is the ratio. At 35 with a 25-year runway, under a third of the full FI number is already enough to coast — which means the decision to stop optimising for income arrives roughly a decade before the decision to stop working. The $260,904.57 cushion is what buys the confidence to act on it.

This is a deterministic planning model, not a guarantee or a recommendation. These simplifications matter when you read the output.

• Everything is in today's dollars at a real rate of return, so there is no inflation input. This is not an omission: inflating the FI number and discounting at a nominal return reduces algebraically to discounting the real FI number at a real return. An inflation field would be a knob that provably changes nothing.
• Returns are applied as one smooth annual rate. There is no volatility and no sequence-of-returns risk, and coasting through a lost decade will land well below this projection — which is the main argument for keeping a cushion above the coast number rather than stopping the moment you cross it.
• Coasting assumes you never sell. Contributions stopping is not the same as withdrawals starting; any money taken out during the coast years breaks the arithmetic entirely.
• Taxes are not modeled. Include your expected retirement tax bill inside annual spending, and remember a dollar in a traditional 401(k) is not a dollar in a brokerage account.
• Spending is assumed constant in real terms — no lumpy costs, no retirement spending smile, no long-term care shock.
• Social Security, pensions, and any other fixed income are not modeled. If you expect them, reduce your annual retirement spending by the amount they will cover from your retirement age onward.
• The expected real return is clamped to a floor of -2% so the discounting stays finite, withdrawal rates to 2%-10%, and ages to whole years. Results are illustrative estimates, not personalised financial, tax, or investment advice.

Coast FIRE

The point where invested assets will compound into a full FIRE number by a target date with no further contributions. It does not mean you stop working — it means work only has to cover current spending, not fund the future too.

The rising coast number

The coast number grows every year at exactly the rate your portfolio does, because the remaining runway shrinks as fast as the balance compounds. The consequence is that with zero contributions your funded ratio never changes: if you are not coasting today, waiting will not get you there.

Real versus nominal return

A real return is what remains after inflation. Working in real terms lets both the FI number and the portfolio be quoted in the same dollars, which is what removes inflation from this calculation entirely.

Safe withdrawal rate and the 25x rule

The share of a portfolio that can be withdrawn annually without depleting it. The 4% figure comes from the Trinity study on 30-year US retirements and implies 25x annual spending; 3.5% implies 28.6x and suits horizons of 40 years or more.

Barista FIRE

A close relative: part-time income covers part of your spending while the portfolio still has to bridge the rest. It needs a different calculation, because the portfolio is being drawn down during the coast years rather than left alone.

• The Coast FIRE CatalystWhy the point where contributions stop mattering is the milestone that actually changes career decisions — with the arithmetic behind it.
• Can I FIRE Yet? CalculatorOnce coasting is settled, check whether you could stop working outright — counting only FIRE-ready assets and modelling a cash bridge.
• Couples FI PlannerModel two partners with different retirement ages, shared and personal expenses, and pension income instead of a single household total.
• All Stoke planning toolsThe full set of free FIRE calculators and planners.