Financial Independence, Retire Early (FIRE) boils down to one number: the size of the investment pile that can throw off enough passive income to cover your living expenses for the rest of your life. This FIRE number calculator works out that target for you using the classic 4% rule from the Trinity Study, then layers on your savings rate and expected investment growth to estimate exactly how many more years of work stand between you and that number.
The math is refreshingly simple. Multiply your annual spending by 25 and you get your FIRE number. From there, the only two levers that move your retirement date are spending less, saving more, and letting compound growth do the heavy lifting. Adjust the inputs below and every figure updates instantly.
How to Use
- Enter your Annual Expenses — what you actually spend in a normal year today, not what you hope to spend. Mortgage or rent, groceries, utilities, insurance, travel, hobbies, and a realistic buffer for surprises all belong here.
- Set your Safe Withdrawal Rate. The default 4.0% comes from the Trinity Study: a 4% initial withdrawal, adjusted for inflation, historically survived a 30-year retirement. If you are retiring at 40 and plan for 50+ years of withdrawals, drop it to 3.5%.
- Add your Current Savings & Investments — everything already invested in retirement accounts, brokerage accounts, and taxable savings that is earmarked for early retirement.
- Type your Gross Annual Income and your Savings Rate. The savings rate is the single most powerful knob on this page: jumping from 20% to 50% cuts your working life roughly in half.
- Set your Expected Annual Return. 7% nominal (about 4–4.5% after inflation) is the long-run average for a diversified 60% stock / 40% bond portfolio during your accumulation years.
- Read the result card. Your FIRE Number is the nest egg you need; Years Until FIRE is how long it will take your current savings plus yearly contributions to reach it, growing at your assumed return.
The FIRE Number Formula
Your target nest egg comes straight from the 4% rule popularized by William Bengen (1994) and the Trinity Study (1998):
FIRE Number = Annual Expenses ÷ Safe Withdrawal Rate
In plain terms, if you spend $60,000 a year and withdraw 4% of your portfolio, you need 60,000 ÷ 0.04 = $1,500,000. In retirement you withdraw $60,000 in year one (about $5,000 per month), raise that amount each year for inflation, and historical market returns keep the portfolio alive for 30+ years.
To estimate how long accumulation takes, the calculator treats your current savings and your yearly contributions as growing at your assumed annual return r. Solving the future-value-of-annuity equation for n gives:
n = ln((FIRE + S/r) / (Current Savings + S/r)) / ln(1 + r)
where S is your annual savings in dollars. With $60,000 of annual spending, a 4% withdrawal rate, zero starting savings, a $120,000 income, a 50% savings rate, and a 7% return, S = $60,000 and the formula gives roughly 14.95 years until FIRE. Notice that a 50% savings rate on a $120,000 income means you live on $60,000 — exactly the income your portfolio will replace, which is the whole point of the exercise.
How Savings Rate Rewrites the Timeline
Your savings rate is far more powerful than your salary or your investment returns. On a fixed $60,000 annual expense and 7% returns:
- 20% savings rate on a $75,000 income: saving $15,000 per year, FIRE takes about 33 years.
- 50% savings rate on a $120,000 income: saving $60,000 per year, FIRE takes about 15 years.
- 70% savings rate on a $200,000 income: saving $140,000 per year, FIRE takes about 9 years.
The reason is arithmetic: a higher savings rate both shrinks your FIRE number (because your expenses are lower) and speeds up deposits at the same time. This is why the FIRE movement obsessively tracks savings rate rather than net worth alone.
Examples
Example 1 — The textbook path. A 32-year-old spends $60,000 a year, saves nothing yet, earns $120,000, and invests 50% of it at 7%. Her FIRE number is $1,500,000, she can withdraw $5,000 per month in retirement, and she reaches the number around age 47 — about 15 years of focused saving.
Example 2 — Starting with a head start. A couple already has $250,000 invested, spends $80,000 a year, earns $150,000, saves 40% ($60,000 a year), and expects a 5.5% return. Their FIRE number is $2,000,000, and thanks to the existing $250,000, they get there in roughly 15.6 years instead of 18.
Example 3 — High-spending household. A family spends $1,200,000 a year, holds $500,000, earns $300,000, saves 60% ($180,000 a year), and nets a 6% return. Their FIRE number is a daunting $30,000,000, and even at that aggressive savings rate the formula projects about 38.5 years. The lesson: lifestyle inflation inflates your FIRE number far faster than salary growth can outrun it.
FAQ
What is a FIRE number?
Your FIRE number is the total investment balance at which a safe annual withdrawal (traditionally 4% of the balance) covers your living expenses for life. The shorthand is annual spending × 25. Spend $60,000 a year and your FIRE number is $1.5 million; spend $100,000 and it is $2.5 million.
How does the 4% rule work?
The 4% rule comes from the Trinity Study, which tested rolling 30-year periods of market history. It found that withdrawing 4% of your nest egg in year one, then raising that withdrawal each year for inflation, survived 30 years in almost all past market environments. A higher withdrawal rate (5%+) works in good markets but raises the risk of running out of money after a bad sequence of early returns.
What savings rate do I need to retire early?
There is no single number, but the classic FIRE rule of thumb is: a 50% savings rate lets you retire in about 15 years, a 25% savings rate in about 32 years, and a 75% savings rate in under 10 years. The calculator above uses your exact income, expenses, and returns to give you a personalized answer rather than a generic rule.
Should I use a 4% or 3.5% withdrawal rate?
Use 4% if you plan to spend roughly 30 years in retirement and can cut spending in a bear market. Use 3.5% (or even 3%) if you are retiring in your 30s or 40s and face a 50–60 year retirement horizon, because your money has to survive more rolling market cycles. Lowering the withdrawal rate from 4% to 3.5% raises your required nest egg by about 14%.
Does this calculator count Social Security or a pension?
No. This is a pure portfolio-based FIRE number. If you expect a pension, Social Security at 62 or 70, rental income, or part-time "barista FIRE" work, subtract those guaranteed flows from your annual expenses before entering them — your portfolio only needs to cover the gap.
What if my savings rate is 0% but I already have a big nest egg?
If your current savings already equal or exceed your FIRE number, the calculator reports roughly zero years to FIRE — you are already financially independent. If you save nothing and are below the number, the years-to-FIRE projection is treated as effectively unreachable, because no compounding happens without contributions.
Disclaimer
This FIRE number calculator is provided for informational purposes only and does not constitute financial, tax, or investment advice. Results assume a constant average return and a fixed withdrawal rate; actual market returns, inflation, taxes, and spending will vary. The 4% rule is a historical guideline, not a guarantee. Always build a buffer and confirm your plan with a qualified financial professional before retiring early.