What is FIRE? Financial independence, retire early
Last reviewed October 17, 2026
FIRE stands for financial independence, retire early. The idea is simple: save and invest a large share of what you earn, until your investments could cover your living costs. From then on, work becomes a choice rather than a necessity. Some people stop working entirely; many keep working, just on their own terms.
FIRE is not a product or a strategy you sign up for. It is a way of looking at one question: how much money would it take for your savings to pay for your life, and how long could it take to get there?
The FIRE number
The starting point is your FIRE number: roughly how big a pot you would need to live off it.
FIRE number = yearly spending ÷ withdrawal rate
With the common 4% withdrawal rate, that is the same as 25 times a year of spending. Someone who spends 1,200 a month (14,400 a year) has a FIRE number of 360,000. Someone who spends 30,000 a year has a FIRE number of 750,000.
Two things follow from this simple formula:
- Spending matters as much as saving. Every 100 a month you no longer need lowers the FIRE number by 30,000 (100 × 12 × 25).
- The number is about spending in retirement, not today. Many people spend less once a mortgage is paid off or children are independent; others plan to travel more. The retirement payment plan on this site lets you set retirement spending as a share of what you spend now.
Where the 4% rule comes from
The 4% rule comes from US research in the 1990s: a 1994 study in the Journal of Financial Planning first put the figure at about 4%, and the 1998 “Trinity study” by three professors at Trinity University in Texas made it widely known. The researchers looked at every 30-year period in past US market data and asked: if you took a fixed share of a portfolio in the first year, then raised that amount with prices every year, how often did the money last?
For portfolios mostly in stocks, taking about 4% in the first year lasted 30 years in the large majority of historical periods. That is where “safe withdrawal rate” comes from. Keep its limits in mind:
- It is a rule of thumb from past data, not a promise. Future returns can be lower than in the past.
- It was built for 30-year retirements. Someone stopping work at 40 might need the money to last 50 years or more, and later research suggests a lower rate gives more room for that.
- The original data is US markets. Studies of other countries’ markets have often found lower historical safe rates.
- A bad first decade matters most: falling markets early in retirement, while you are taking money out, do more damage than the same fall later on.
So the 4% rule is a useful way to size a goal, not an exact answer. Our calculator shows the 4% rule next to your own plan so you can see the difference.
How compound interest gets you there
FIRE leans on compound interest: money that earns a return, then earns a return on that return. Over long periods, growth starts to outweigh what you put in yourself.
Take a plan of 1,000 to start and 200 a month, growing 10% a year with monthly compounding. After 30 years you would have put in 73,000, and the pot would be about 471,935. In year 13, what the money has earned overtakes what you put in, and from then on the curve bends upward. At the 4% rule, a pot of that size could pay about 1,573 a month.
These numbers assume a steady 10% a year with no fees, tax or inflation. Real markets go up and down, and once you switch on inflation (2.5% a year), the same pot is worth about 224,992 in today’s money. The calculator lets you add fees, tax, inflation and market risk one at a time to see what each one changes.
Savings rate: the lever people talk about
In FIRE circles the main lever is the savings rate: the share of take-home pay you put away. A higher savings rate works twice. More money goes in, and the life you have to pay for later costs less, so the FIRE number itself is lower.
The exact time it takes depends on returns, fees, tax and inflation, which no one knows in advance. What the arithmetic does show is that at low savings rates, small changes barely move the date, and at high savings rates, every extra few percent can shorten the road by years.
The flavours of FIRE
Over time the community has named a few variations. They differ in how much spending the pot has to cover and whether some work continues.
| Name | What it means |
|---|---|
| Lean FIRE | Financial independence on a frugal budget. A smaller FIRE number, less room for surprises. |
| Fat FIRE | Financial independence with a comfortable budget. A much larger FIRE number. |
| Barista FIRE | Leaving full-time work and covering part of your costs with part-time or lower-paid work, so the pot only needs to cover the rest. |
| Coast FIRE | Having saved enough early that, without adding more, the pot could grow into your FIRE number by a normal retirement age. You still work to pay today’s costs, but you no longer need to save for retirement. |
Coast FIRE is compound interest run backwards; we explain it step by step on the Coast FIRE calculator.
What FIRE is not
- Not a get-rich-quick idea. Most FIRE plans take one or two decades of steady saving.
- Not a single number that settles everything. Health costs, pensions, taxes, housing and family plans all differ, and they change over time.
- Not advice. The numbers on this site are illustrations of how money could grow under the assumptions you choose. They do not tell you what to do with your money.
Try it with your own numbers
Start with the compound interest calculator to see how your savings could grow. Then open the retirement calculator to see your FIRE number, how long your pot could last, and how your plan compares with the 4% rule. Every formula is described in our methodology.
Educational content, not financial advice. All results are illustrations based on the assumptions you enter; real returns vary and past returns do not promise future ones.