Coast FIRE calculator
Find the invested balance that lets compound growth fund your retirement with zero further contributions — and the age you'll cross that line at your current savings rate. Everything is expressed in today's dollars.
What is a Coast FIRE calculator?
A Coast FIRE calculator finds the invested balance that will grow to your full retirement number by itself — no more contributions — by your target retirement age. It divides your annual spending by a safe withdrawal rate to get your FIRE number, then discounts it back to today at your inflation-adjusted return. If your portfolio is above that line, retirement is already funded; you just have to leave it alone.
Your path to the coast line.
| Period | Contributed | Balance | Coast target | Coast progress |
|---|---|---|---|---|
| Age 31 | $112,000 | $116,309 | $384,422 | 30% |
| Age 32 | $124,000 | $133,284 | $400,128 | 33% |
| Age 33 | $136,000 | $150,952 | $416,476 | 36% |
| Age 34 | $148,000 | $169,343 | $433,492 | 39% |
| Age 35 | $160,000 | $188,484 | $451,202 | 42% |
| Age 36 | $172,000 | $208,408 | $469,637 | 44% |
| Age 37 | $184,000 | $229,146 | $488,824 | 47% |
| Age 38 | $196,000 | $250,731 | $508,796 | 49% |
| Age 39 | $208,000 | $273,198 | $529,583 | 52% |
| Age 40 | $220,000 | $296,583 | $551,220 | 54% |
| Age 41 | $232,000 | $320,923 | $573,740 | 56% |
| Age 42 | $244,000 | $346,258 | $597,181 | 58% |
| Age 43 | $256,000 | $372,628 | $621,579 | 60% |
| Age 44 | $268,000 | $400,075 | $646,975 | 62% |
| Age 45 | $280,000 | $428,643 | $673,408 | 64% |
| Age 46 | $292,000 | $458,379 | $700,920 | 65% |
| Age 47 | $304,000 | $489,330 | $729,557 | 67% |
| Age 48 | $316,000 | $521,545 | $759,364 | 69% |
| Age 49 | $328,000 | $555,076 | $790,389 | 70% |
| Age 50 | $340,000 | $589,978 | $822,681 | 72% |
| Age 51 | $352,000 | $626,305 | $856,292 | 73% |
| Age 52 | $364,000 | $664,116 | $891,277 | 75% |
| Age 53 | $376,000 | $703,472 | $927,691 | 76% |
| Age 54 | $388,000 | $744,437 | $965,593 | 77% |
| Age 55 | $400,000 | $787,074 | $1,005,043 | 78% |
| Age 56 | $412,000 | $831,454 | $1,046,105 | 79% |
| Age 57 | $424,000 | $877,647 | $1,088,845 | 81% |
| Age 58 | $436,000 | $925,728 | $1,133,331 | 82% |
| Age 59 | $448,000 | $975,772 | $1,179,634 | 83% |
| Age 60 | $460,000 | $1,027,861 | $1,227,829 | 84% |
| Age 61 | $472,000 | $1,082,079 | $1,277,993 | 85% |
| Age 62 | $484,000 | $1,138,511 | $1,330,207 | 86% |
| Age 63 | $496,000 | $1,197,250 | $1,384,554 | 86% |
| Age 64 | $508,000 | $1,258,388 | $1,441,121 | 87% |
| Age 65 | $520,000 | $1,322,023 | $1,500,000 | 88% |
Discounting your FIRE number back to today.
Coast FIRE math is two familiar formulas chained together. Your FIRE number is annual retirement spending divided by a safe withdrawal rate — the classic 4% rule turns $60,000 of spending into a $1,500,000 target. Your coast number is that target discounted back to today at your expected growth rate: whatever balance, compounded for the years you have left, lands exactly on the target.
This calculator keeps every figure in today's dollars, which means the growth rate must be the real return — (1 + nominal) ÷ (1 + inflation) − 1, about 4.1% when markets return 7% and inflation runs 2.8%. Mixing today's spending with a nominal 7% discount is the classic mistake: it produces a coast number roughly 60% too low over a 35-year horizon, because it ignores that $1.5M in 2061 buys far less than $1.5M today.
The discounting is why time is the dominant variable. At a 4.1% real return, a 25-year-old needs only about $302,000 to coast to a $1.5M retirement at 65, a 35-year-old needs about $451,000, and a 50-year-old needs about $822,000. Every decade you delay roughly halves the work compounding can do for you.
- S
- Annual spending — what retirement costs per year, in today's dollars
- SWR
- Safe withdrawal rate — typically 3.25–4% — S ÷ SWR is your FIRE number
- r
- Real return — nominal return adjusted for inflation, (1+nom)/(1+inf) − 1
- n
- Years to retirement — target retirement age minus your current age
Six ways to actually use these numbers.
Use real returns, always.
A 7% nominal return with 2.8% inflation is a 4.1% real return. Discounting at 7% while keeping spending in today's dollars understates your coast number by ~60% over 35 years.
Stress-test the SWR.
Moving from 4% to 3.5% raises a $60K-spending FIRE number from $1.5M to $1.71M — and your coast number with it. Long early retirements deserve the conservative end.
Only invested money counts.
Home equity you live in and cash earning below inflation don't compound toward your target. Count brokerage, 401(k), IRA, and HSA balances.
Coasting is a checkpoint, not a cliff.
Crossing the line means retirement is funded if markets deliver your assumed return. Re-run the numbers yearly; a bear market can pull you back under the line.
Contributions still buy freedom.
After coasting, every extra dollar saved moves your retirement age earlier instead of funding the baseline. That's often worth more than the spending it displaces.
Spending is the biggest lever.
Cutting planned retirement spending by $10K/year cuts your FIRE number by $250K at a 4% SWR — and your coast number by the same proportion. No return assumption is that powerful.