What the FIRE number is
Your FIRE number is the size of an investment portfolio that can pay your yearly expenses for the rest of your life. Once you reach it, working becomes a choice. The idea is the backbone of the FIRE movement ("financial independence, retire early"), but it is useful for anyone who wants to know when work could become optional.
The number comes from a safe withdrawal rate: the share of your portfolio you can spend in the first year of retirement, then adjust for inflation each year after, with a high chance the money lasts. The well-known 4% rule comes from US research on historical stock and bond returns over 30-year retirements.
How this FIRE calculator works
- It divides your yearly spending by the withdrawal rate to get your target. At 4% that is 25 times your spending.
- It converts your expected return into a real, after-inflation return, so the target stays in today's dollars.
- Starting from your current savings, it adds your monthly investment and a month of growth, again and again, until the balance reaches the target. The number of months it takes is your time to financial independence.
If you enter your take-home pay, it also shows your savings rate, the single biggest lever on how fast you get there. Someone saving 50% of take-home pay can often reach FIRE in well under 20 years, while a 10% savings rate typically takes a full career.
The formula
Worked example
Jordan spends $40,000 a year and wants to plan with a 4% withdrawal rate, so the FIRE number is $40,000 × 25 = $1,000,000.
Jordan has $50,000 invested and adds $2,500 a month ($30,000 a year). With 7% returns and 3% inflation (a real return of about 3.9%), the balance reaches $1,000,000 in about 20 years. On $6,000 a month of take-home pay, that is a savings rate of about 42%.
How to reach FIRE faster
- Spend less. Cutting spending works twice: it raises how much you can save and it lowers the target. Every $1,000 of yearly spending you drop reduces a 4% FIRE number by $25,000.
- Raise income. Raises and side income help most when the extra money is invested rather than spent.
- Keep costs low. Fund fees and taxes come straight out of your return. Tax-advantaged accounts such as a 401(k), IRA or HSA can make a big difference over decades.
- Stress-test it. Try a lower return and a 3.5% withdrawal rate. If the plan still works, it is much more robust.
Frequently asked questions
Is the 4% rule still safe?
It is a reasonable starting point, not a guarantee. It was based on 30-year retirements using US market history. If you retire in your 30s or 40s, your money may need to last 50 years or more, so many planners suggest 3.25% to 3.5% for very early retirees.
Should I use real or nominal returns?
Enter the nominal return and inflation separately and the calculator converts them for you. Because the FIRE number is in today's dollars, the projection uses the after-inflation return.
What counts as savings for FIRE?
Count investments that can pay for living costs: retirement accounts, brokerage accounts and cash set aside for investing. Most people leave out their home equity unless they plan to sell and downsize.
What is Lean FIRE and Fat FIRE?
They are informal labels for budget levels. Lean FIRE usually means retiring on a modest budget, often under about $40,000 a year, while Fat FIRE means a larger, more comfortable budget, often $100,000 a year or more. The math is the same; only the spending input changes.
Does this account for taxes?
Not directly. If your withdrawals will be taxed, enter your spending including the tax you expect to pay, or use a slightly lower withdrawal rate.
Last reviewed November 2026. Spotted an error? Tell us.