What is FIRE?

FIRE in one paragraph

FIRE stands for Financial Independence, Retire Early. You reach it when your investments can pay for your yearly spending indefinitely, usually once you have about 25 times that spending invested. After that, work is a choice, not a necessity.

People get there by saving a large share of their income and investing it in low-cost funds for many years. How many depends mostly on your savings rate: at 50% of take-home pay, it takes about 17 years from a standing start. Along the way there are useful milestones, and there are versions of FIRE for frugal budgets, generous budgets and people who still want to work part-time. This guide explains all of them with one consistent example.

Where FIRE came from

The ideas behind FIRE are older than the acronym. The book most often credited as its starting point is Your Money or Your Life by Vicki Robin and Joe Dominguez, first published in 1992. Dominguez, a former Wall Street analyst, stopped working for pay in 1969 and taught a nine-step program for changing how you think about earning and spending. The aim is to change your relationship with money, so that what you earn and spend reflects what you value. By 1997 the book had sold more than half a million copies in English. A revised edition came out in 2018.

The math side comes from retirement research. In 1994 financial planner William Bengen found that withdrawing 4% of a portfolio in the first year, then raising that amount with inflation, lasted at least 30 years in every historical US period he tested. The Trinity study of 1998 reached similar conclusions. That is where the "25 times your spending" rule of thumb comes from.

Blogs turned these ideas into a movement. Mr. Money Mustache, written by a man who retired at 30, started in 2011. His 2012 post "The Shockingly Simple Math Behind Early Retirement" showed that the share of your income you save, not the size of your income, decides how long it takes. Online forums and other blogs then added the variations described below.

Your FIRE number

Every type of FIRE starts from one figure: how much you need invested to live off your portfolio.

The 4% rule was tested on 30-year retirements. If you stop working at 40, your money may need to last 50 years, so many people use a lower rate. Research on 60-year retirements suggests 3.25% to 3.5% is more cautious, and Morningstar puts a safe starting rate at 3.9% even for 30 years. Our guide to the 4% rule goes through the research in detail.

Two details make the number honest. First, your spending should include the taxes you'll pay on withdrawals and, in the US, health insurance before Medicare. Second, be careful with pensions. Subtracting a pension from your spending only works if you'll retire around the age it starts. If you retire earlier, you also need money to bridge the gap years before it begins. Our guides to Social Security, CPP and OAS and the UK State Pension show how to handle that gap. The FIRE number calculator does the arithmetic for any spending level and withdrawal rate.

Why your savings rate matters most

Your savings rate is the share of your take-home pay you invest. It works twice. A higher rate means more money going in, and it also means you live on less, so the amount you need at the end is smaller.

The table below starts from nothing invested, assumes you keep the same spending in retirement, a 7% return with 2.5% inflation (4.39% a year after inflation) and a 4% withdrawal rate. The result is the same whether you take home $50,000 or $150,000, because both your saving and your FIRE number scale with income.

Going from a 10% to a 20% savings rate cuts about 16 years. Going from 50% to 60% cuts about four and a half. Mr. Money Mustache's table shows slightly shorter times because it assumes a 5% return after inflation; ours uses 4.39% to leave a margin. Existing savings shorten every figure.

Here is the double effect in dollars. A household taking home $60,000 and saving 25% lives on $45,000, so it needs $1,125,000 and gets there in 33 years 7 months. If it saves 40% instead, it lives on $36,000, needs only $900,000, and gets there in 22 years 5 months. Saving an extra $9,000 a year takes more than 11 years off the journey.

The five types of FIRE

The labels below are conventions from the FIRE community, not formal definitions. The spending lines between them are rough, and they depend on where you live and how many people you support.

Regular FIRE

Your investments cover a normal, comfortable budget for your household, and you stop working whenever you like. This is what most people mean by FIRE.

Lean FIRE

Financial independence on a frugal budget. The FIRE number is smaller, so you get there sooner, but there's little room to cut back if markets fall. Compare it with the generous version in Lean FIRE vs Fat FIRE, or run the Lean FIRE calculator.

Fat FIRE

Financial independence with a large budget for travel, a bigger home, private schooling or simply more slack. It takes much longer unless your income is high. The Fat FIRE calculator shows how long.

Coast FIRE

You have enough invested that, without adding another dollar, growth alone will reach your full FIRE number by a normal retirement age. You keep working to pay today's bills, but you can stop saving for retirement. Our guide on what Coast FIRE is covers it in depth.

Barista FIRE

Your investments cover part of your spending now, and part-time or lower-paid work covers the rest. The name refers to a relaxed job such as working in a coffee shop. See Coast FIRE vs Barista FIRE for how the two compare.

One person, five versions of FIRE

Here is how each type plays out for Alex, our standard example: 32, with $185,000 invested and $1,500 a month going in, using our default assumptions. Alex keeps saving the same amount in every case; only the target changes.

A few things stand out:

• The milestones arrive in order. Coast FIRE comes first because nothing is withdrawn until 60. Barista FIRE comes next because part-time pay covers half the budget.
• Barista FIRE is the most fragile milestone. The $500,000 figure assumes the $20,000 of part-time pay continues and that a 4% withdrawal rate holds over a very long horizon; for retirements of 40 years or more, our 4% rule guide suggests 3% to 3.5%. If Alex stopped saving at 41 and withdrew $20,000 a year while earning the expected return, the portfolio would be about $546,000 at 60, not the $1,000,000 needed to stop working entirely. Going part-time early works best if you keep earning that income, or save again later.
• Spending sets the finish line. Living on $30,000 instead of $40,000 brings full independence forward by four and a half years.
• Fat FIRE needs a fatter savings rate. On $1,500 a month, a $100,000 budget isn't early retirement at all. Saving $5,000 a month instead, Alex would reach $2,500,000 in 21 years 1 month, at 53.

Many people pass through several of these. A common path is to reach Coast FIRE, keep working while the portfolio grows, switch to part-time work at Barista FIRE, and stop entirely at full FIRE.

What FIRE is not

• It isn't only about quitting work. Plenty of people who reach financial independence keep working, start a business, or move to work they enjoy but that pays less. The point is that work becomes optional.
• It isn't a promise. The math uses average returns. Real markets have bad decades, and the order of good and bad years matters, especially in the first years after you stop. Our guide to sequence of returns risk explains why.
• It isn't just extreme frugality. Cutting spending is the most powerful lever, but earning more, cutting investment fees and choosing a realistic target all help. Even a 0.5% yearly fee can delay your date by years.
• It isn't all or nothing. Coast and Barista FIRE give you real freedom long before the full number.

Which type fits you?

The right target depends less on math than on what you want your life to look like. Some questions to ask yourself:

• Do you want to stop working, or change how you work? If you like your field but not the pressure, Coast FIRE may give you most of what you want years sooner. If you want your weekdays back, look at Barista or full FIRE.
• How much do you really spend, and how much would you miss? If your current budget already feels lean, a lean target leaves no slack. If you could happily live on less, the time saved is large, as the table above shows.
• How secure is your income? A high, steady income makes Fat FIRE reachable. A variable one makes the early milestones, which don't depend on selling investments, more valuable.
• Who depends on you? Children, aging parents and health costs all belong in your spending. In the US, leaving a job often means buying your own health insurance until Medicare, and that cost can be large.

You don't have to choose once. Plans change as careers, families and markets do. Recalculating once a year keeps your target honest.

How to get started

1. Track your spending for a few months. Your FIRE number is built on it, so it needs to be real, not a guess.
2. Work out your FIRE number. Divide the spending you expect in retirement by a withdrawal rate between 3.5% and 4%.
3. Find your savings rate. Divide what you invest each month by your take-home pay, then use the table above to see roughly how far away you are.
4. Use low-cost, diversified investments and tax-advantaged accounts where you can.
5. Check your Coast FIRE date. It's often closer than people expect, and knowing it changes how work feels.

Our methodology page explains every formula and assumption our calculators use, so you can check the numbers in this guide yourself.

Sources

The worked examples are our own calculations, explained on our methodology page. History and research come from:

1. History of Your Money or Your Life. Vicki Robin. The book was first published in 1992 by Viking/Penguin and was updated in 2018.
2. Your Money or Your Life (revised edition). Vicki Robin and Joe Dominguez, Penguin Random House, 2018. The current edition, revised for 2018 with a foreword by Mr. Money Mustache.
3. Joe Dominguez, Living-Simply Guru. The Seattle Times, 1997. Dominguez left paid work in 1969; the book, built on his nine-step program, had sold more than half a million English copies by 1997.
4. Meet Mr. Money Mustache. Mr. Money Mustache, 2011. The blog's first post, by a writer who retired at 30.
5. The Shockingly Simple Math Behind Early Retirement. Mr. Money Mustache, 2012. Showed that your savings rate, not your income, sets how long it takes to reach financial independence.
6. Determining Withdrawal Rates Using Historical Data. William P. Bengen, Journal of Financial Planning, 1994. The original 4% rule: a 4% first-year withdrawal, raised each year with inflation, lasted at least 30 years in every historical US period studied.
7. Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable. Philip L. Cooley, Carl M. Hubbard and Daniel T. Walz, AAII Journal, 1998. The “Trinity study”: withdrawals of 3% to 4% rarely ran out of money over periods of up to 30 years with a mix of stocks and bonds.
8. The Ultimate Guide to Safe Withdrawal Rates, Part 1: Introduction. Early Retirement Now, 2016, updated 2024. Safe withdrawal rates for 60-year retirements average more than a percentage point below 30-year ones; it concludes that “3.5% is the new 4%.”
9. What’s a Safe Retirement Withdrawal Rate for 2026?. Morningstar. Puts a safe starting withdrawal rate at 3.9% for a 30-year retirement, with a 90% chance of success.
10. HealthCare.gov. US Centers for Medicare & Medicaid Services. Where US residents without workplace coverage can compare health insurance plans.