Coast FIRE calculator
By Jude Wallis
Coast FIRE asks whether what you already have will grow into your FIRE number with no further deposits. $200,000 at 7 percent for 20 years becomes $773,936.89. A $40,000 spend at a 4 percent withdrawal rate needs $1,000,000, so the gap is $226,063.11.
Grown nest egg
$773,936.89
FIRE number $1,000,000.00. Gap $226,063.11.
- FIRE number
- $1,000,000.00
- Grown nest egg
- $773,936.89
- Gap to FIRE
- $226,063.11
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On this page
The formula
is annual spending and the withdrawal rate, so is the FIRE number. is what current savings grow to at rate over years with nothing added.
Two independent numbers, then a subtraction
The target comes from spending: $40,000 a year at a 4 percent withdrawal rate needs $1,000,000, because 4 percent of a million is forty thousand. The other number comes from growth: $200,000 compounding at 7 percent for 20 years reaches $773,936.89 without another deposit.
Neither number knows about the other. The gap of $226,063.11 is simply what is missing, and it is stated in today's dollars at the future date rather than as a savings rate. The FIRE number calculator builds the target on its own.
Coasting is about deposits, not about work
Reaching coast FIRE means the existing balance no longer needs help to arrive on time. It says nothing about stopping work; it says the saving part of work is optional from that point. Many people reach coast long before they reach the number itself, because 20 years of compounding does more than 20 years of contributions at this kind of balance.
That is the actual insight the arithmetic offers. Between here and the target, $773,936.89 of the $1,000,000 arrives from growth on money already saved.
The two rates are assumptions, and they are not the same kind
The 7 percent growth rate is a nominal expectation over 20 years, which is a long horizon and a wide range. The 4 percent withdrawal rate is a spending rule, not a market forecast. Changing the first moves the balance; changing the second moves the target.
A second case makes the sensitivity visible: $100,000 at 6 percent for 25 years reaches $429,187.07 against a $750,000 target for $30,000 of spending, leaving $320,812.93. More years, lower rate, smaller starting balance, larger gap. See how real returns work for the inflation question underneath both rates.
What the gap tells you
This compares one balance growing at one rate against one spending target, at a single future date. It is a checkpoint rather than a plan: it answers whether today's savings alone reach the target, and by how much they miss. How FIRE numbers work covers the withdrawal rate behind the target, and present value is the same arithmetic run backwards. This is educational material, not financial advice.
Worked examples
\$200,000 coasting for 20 years
Savings are $200,000, expected growth is 7 percent, the horizon is 20 years, spending is $40,000 a year and the withdrawal rate is 4 percent. What is the gap?
- FIRE number: .
- Coast value: .
- Gap: .
The target is $1,000,000, the $200,000 grows to $773,936.89 on its own, and the gap is $226,063.11.
A longer horizon at a lower rate
$100,000 at 6 percent for 25 years, with $30,000 of spending at a 4 percent withdrawal rate.
- FIRE number: .
- Coast value: .
- Gap: .
The target is $750,000, the balance coasts to $429,187.07, and $320,812.93 is still missing.
Reading the coast value as a retirement date
$773,936.89 at year 20 is what the current balance becomes if nothing is added. It is not a projection of the whole plan, because future contributions are deliberately excluded. The gap of $226,063.11 is exactly the part those contributions still have to cover.
Common questions
What does coast FIRE actually mean?
That existing savings will reach the target on their own by the chosen date, so further contributions are optional rather than required.
Why is the withdrawal rate 4 percent here?
It is the input this example uses to turn spending into a target. Enter whatever rate the plan assumes.
Is this financial advice?
No. It is educational material comparing a compounded balance to a spending target.
Keep reading
This page is educational material, not financial advice. The figures come from the formula shown and assume the inputs you enter hold for the whole term. Your own rate, fees, taxes and timing will differ, so treat the output as arithmetic to check a decision against, not as a recommendation.