What is Coast FIRE?
Coast FIRE means you have invested enough that, without adding another dollar, your money can grow into what you need by the age you want to retire, assuming the return you expect. From then on, your paycheck only has to cover your bills. Your Coast FIRE number is that amount, measured today.
Last reviewed
How the calculator works
The calculator answers two questions. The first is the classic one: how much would you need invested today to stop saving now? The second is about the plan you actually have: if you keep saving at your current rate, at what age can you stop?
Your FIRE number
Everything starts from the amount you need on the day you retire fully. Without any pension or Social Security, it's your yearly spending divided by your withdrawal rate.
FIRE number = yearly spending ÷ withdrawal rate$50,000 a year at a 4% withdrawal rate is $1,250,000. That's 25 times your spending.
When you add Social Security or a pension, the calculator works out the gap your savings have to fill in each year of retirement and adds those gaps up, so income that starts a few years after you retire still counts. How we calculate shows the exact method.
Your Coast FIRE number
Coast FIRE number = FIRE number ÷ (1 + r) ^ (R − A)This is the FIRE number discounted back to today: the amount that would grow into it by your retirement age with nothing added and nothing taken out.
- r is your yearly return after inflation and after fees. The default is 5%.
- R is the age you want to retire fully.
- A is your age today.
If what you have invested is at least your Coast FIRE number, you could stop saving today and still reach your FIRE number on time, as long as the return holds and your paycheck covers your spending until then.
The age you can stop saving
Most people haven't reached their Coast number yet, so the calculator also looks at the saving you're already doing. It tries each age from today onward and picks the earliest one where the balance you'd have by then is enough to reach your FIRE number on its own. That's the age shown in the result, along with the calendar year.
All amounts are in today's dollars. A $50,000 budget means what $50,000 buys now, so the return you enter is the return after inflation. If you'd rather enter a return before inflation, switch the return field to nominal and the calculator converts it for you.
Three worked examples
Example 1: the numbers the calculator opens with
A 35-year-old has $300,000 invested and saves $15,000 a year. They want to retire fully at 60 and spend $50,000 a year, and they expect 5% a year after inflation.
| Age today | 35 |
|---|---|
| Invested today | $300,000 |
| Saving per year | $15,000 |
| Retire fully at | 60 |
| Spending per year in retirement | $50,000 |
| Return after inflation | 5% |
| Withdrawal rate | 4% |
| FIRE number at 60 | $1,250,000 |
|---|---|
| Coast FIRE number today | $369,128 |
| Progress toward it | 81.3% |
| Can stop saving at | 41 |
| Calendar year | 2032 |
| Invested at that point | $504,057 |
$1,250,000 is $50,000 divided by 4%. Discounted back 25 years at 5% a year, that's $369,128 today, so the $300,000 already invested covers 81.3% of it. Saving $15,000 a year for six more years brings the balance to $504,057 at 41, and that grows to at least $1,250,000 by 60 with nothing more added.
Example 2: the same person, counting Social Security
Now the same person expects $24,000 a year from Social Security starting at 67, after tax and in today's dollars. Their savings only have to fill the gap: all of the $50,000 from 60 to 66, then the part Social Security doesn't cover.
| Age today | 35 |
|---|---|
| Invested today | $300,000 |
| Saving per year | $15,000 |
| Retire fully at | 60 |
| Spending per year in retirement | $50,000 |
| Social Security | $24,000 a year from 67 |
| Return after inflation | 5% |
| Withdrawal rate | 4% |
| FIRE number at 60 | $807,252 |
|---|---|
| Withdrawals per year from 67 | $26,000 |
| Coast FIRE number today | $238,384 |
| Progress toward it | 100% |
| Can stop saving at | 35 (today) |
Counting Social Security cuts the FIRE number by about a third. It isn't simply $26,000 divided by 4%, because the seven years before Social Security starts still have to be paid for in full. The $300,000 already invested is more than the $238,384 Coast number, so on these assumptions this person could stop saving today. Leave Social Security out, as many calculators do, and the answer becomes six more years of saving.
Example 3: starting at 45
A 45-year-old has $150,000 invested, saves $20,000 a year, and wants to retire at 65 on $45,000 a year.
| Age today | 45 |
|---|---|
| Invested today | $150,000 |
| Saving per year | $20,000 |
| Retire fully at | 65 |
| Spending per year in retirement | $45,000 |
| Return after inflation | 5% |
| Withdrawal rate | 4% |
| FIRE number at 65 | $1,125,000 |
|---|---|
| Coast FIRE number today | $424,001 |
| Progress toward it | 35.4% |
| Short at 65, saving the whole way | $65,686 |
| Extra saving per year to close the gap | $1,987 |
Even saving $20,000 every year until 65, this plan ends up $65,686 short of $1,125,000, so there's no age yet at which this person can stop. Saving $1,987 more a year would close the gap. So would retiring a little later or planning to spend a little less, and the calculator shows each of those as you change the numbers.
Checking the plan against market history
The main result assumes the same return every year. Real markets don't behave that way, and a bad decade right after you stop saving hurts more than the same decade later on. So the calculator also runs your plan through every stretch of US market history since 1871 that's long enough to cover it, and through 10,000 Monte Carlo runs built from the same data.
The history card reports two things: how often your whole plan lasted to the end, and how often the classic Coast number, left alone, grew into the FIRE number by your retirement age. For runs that failed, it also shows the age the money ran out.
Why Coast FIRE calculators give different answers
Put the same numbers into five Coast FIRE calculators and you can get five different answers. Usually none of them is wrong. They make different assumptions, and these are the ones that matter most.
- Return before or after inflation. Some calculators take a 7% return and subtract 3% inflation to get 4%. The exact figure is 1.07 ÷ 1.03 − 1, or 3.88%. The difference looks small, but over 25 years it moves the Coast number by a few percent.
- Withdrawal rate. A 4% rate means you need 25 times your spending. At 3.5% you need about 28.6 times, which raises the FIRE number and the Coast number by about 14%.
- Future income. Most simple calculators leave out Social Security and pensions. As Example 2 shows, that can be the biggest difference of all.
- Saving until you coast. The classic formula assumes you stop saving today. Our plan result assumes you keep saving at your current rate until the Coast age, which is usually closer to what people actually do.
- Fees. We take fees out of the return once. A tool that ignores them, or takes them out twice, will be off in one direction or the other.
- Timing within the year. We take withdrawals at the start of each year and add contributions at the end, which is slightly conservative. Tools that assume monthly deposits will show a little more growth.
What this calculator doesn't do
A Coast FIRE number is a planning estimate, and this calculator keeps some things simple on purpose. These are the gaps worth knowing about.
- Taxes are one flat rate on withdrawals. There are no tax brackets, Roth conversions, required minimum distributions or state taxes.
- The main result uses one steady return. The history check shows what varying returns did, but no one knows which sequence you'll get.
- Money moves once a year: withdrawals at the start, contributions at the end.
- Social Security and pension amounts are whatever you enter. The calculator doesn't estimate them or adjust them for claiming early or late.
- It doesn't model death or survivor benefits. Both partners are assumed to live to the end of the plan.
- Health insurance before 65 is a flat yearly amount you enter. There's no estimate of premiums or subsidies.
- Country presets for Canada, the UK and Australia change labels and defaults only. The historical check still uses US market data.
The methodology page covers each of these in more detail.
Common questions
How do I calculate my Coast FIRE number?
Work out your FIRE number first: yearly spending in retirement divided by your withdrawal rate. Then divide that by (1 + r) raised to the number of years until you retire, where r is your expected return after inflation. The calculator above does both steps and also accounts for any pension income you add.
How much do I need to coast at 30?
It depends on what you'll spend and when you'll retire. As one example: to spend $40,000 a year from age 65, with a 5% return after inflation and a 4% withdrawal rate, a 30-year-old needs $181,290 invested today. The same plan at 40 needs $295,303, because the money has 10 fewer years to grow.
What return should I assume?
The default is 5% a year after inflation and before fees. Popular calculators use anywhere from about 4% to 7%. Lower is safer. The sensitivity table under the result shows your Coast number at returns from 3% to 7%, so you can see how much the answer depends on this one input.
Does Coast FIRE mean I can stop working?
No. It means you could stop saving for retirement. Until you retire, your income still has to cover everything you spend. Some people use the room to take a lower-paid job or work fewer hours. If part-time work is the plan, the Barista FIRE calculator is built for it.
What's the difference between Coast FIRE and Barista FIRE?
With Coast FIRE you keep working enough to pay your bills and leave your investments alone. With Barista FIRE you work part-time and your savings help cover the gap, so you need more invested when you make the switch. What is Coast FIRE? compares the different kinds of FIRE.
Should I stop saving once I reach my Coast number?
That's your call, and the calculator can't make it for you. If you stop and returns come in below your assumption, you would need to save again later or retire later. Many people keep saving something as a buffer. You can enter a smaller yearly amount to keep saving after the Coast age and see what it does to your plan.
Is my information stored anywhere?
No. The calculator runs in your browser and your numbers never reach our servers. Saved plans stay in your browser, and share links keep the numbers in the part of the address that browsers don't send. The privacy policy has the details.
Sources
- Cooley, Philip L., Carl M. Hubbard and Daniel T. Walz. "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal, February 1998. Usually called the Trinity study.
- Jeske, Karsten (Early Retirement Now). The Safe Withdrawal Rate Series. earlyretirementnow.com/safe-withdrawal-rate-series
- Shiller, Robert J. Monthly US stock prices, dividends, earnings, consumer prices and long-term interest rates since 1871. shillerdata.com
- US Social Security Administration. Retirement benefits. www.ssa.gov/benefits/retirement
- US Social Security Administration. my Social Security (your personal benefit estimate). www.ssa.gov/myaccount
- Government of Canada. Canada Pension Plan. www.canada.ca/en/services/benefits/publicpensions/cpp.html
- Government of Canada. Old Age Security. www.canada.ca/en/services/benefits/publicpensions/old-age-security.html
- GOV.UK. The new State Pension. www.gov.uk/new-state-pension
- GOV.UK. Check your State Pension forecast. www.gov.uk/check-state-pension
- Services Australia. Age Pension. www.servicesaustralia.gov.au/age-pension