Use actual expenses and include irregular costs such as repairs and healthcare.
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$
$
%
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The classic FIRE assumption is 4% (the "4% rule").
Your FIRE Number
$0
25× your annual expenses
Time to FIRE
—
At your current pace
Annual Investment
$0
What you set aside / year
Portfolio vs. FIRE Number
Portfolio
FIRE Number
My FIRE Plan — Financial Depth
financialdepth.com/fire-calculator
Quick Summary (TL;DR)
- Your FIRE number = annual expenses ÷ withdrawal rate. At the classic 4% rule, that's 25 × your yearly spending.
- Example: $40,000/year of spending → a $1,000,000 target.
- The two biggest levers are your savings rate and your expenses — cutting spending lowers the target and frees up cash to invest.
- Formula:
FIRE Number = Annual Expenses ÷ (Withdrawal Rate ÷ 100)
What Your FIRE Number Really Means
Your FIRE number is the size of portfolio that can fund your lifestyle from investment returns alone — the moment work becomes optional. It rests on the 4% rule, drawn from the Trinity Study: if you withdraw 4% of your portfolio in your first year of retirement and adjust that amount for inflation each year after, history suggests the money has a strong chance of lasting 30+ years. Because 1 ÷ 0.04 = 25, a 4% rate means your target is simply 25 × your annual expenses.
This calculator takes your spending and withdrawal rate to set the target, then projects your current portfolio forward — compounding monthly at your expected return and adding your contributions — until it crosses that line. The formula for the target is FIRE Number = Annual Expenses ÷ (Withdrawal Rate ÷ 100).
Worked example: If you spend $40,000 a year and use a 4% rate, your FIRE number is $1,000,000. Starting with $50,000 invested and adding $2,000/month at a 7% return, you'd reach it in roughly 16–17 years. Trim expenses to $32,000 and the target drops to $800,000 — shaving years off the journey, because cutting spending lowers the goal and frees up cash at the same time.
Frequently Asked Questions
What is a FIRE number?+
It's the portfolio size you need so that returns can cover your living expenses indefinitely, letting you retire early. It equals your annual expenses divided by your safe withdrawal rate — at a 4% rate, that's 25 times your yearly spending.
Why multiply annual expenses by 25?+
The 25× multiplier comes from the 4% rule (Trinity Study), which found that withdrawing 4% in year one and adjusting for inflation afterward had a very high chance of lasting 30+ years. Since 1 ÷ 0.04 = 25, a 4% rate implies 25 times your annual expenses.
How can I reach my FIRE number faster?+
The biggest levers are raising your savings rate and lowering your expenses — and lower expenses help twice, since they free up cash to invest and shrink the target itself. A higher return helps too, but it's less reliable than what you can control.
Key Considerations Before You Trust the Number
The 25× rule is a starting point, not a finish line. A few real-world factors can meaningfully change the target:
- Sequence-of-returns risk. A market crash in your first few years of retirement does far more damage than the same crash later, because you're selling assets while they're down. Two retirees with identical average returns can land in very different places depending on when the bad years hit.
- A longer retirement may need a lower rate. The 4% rule was tested mostly on 30-year retirements. If you retire in your 30s or 40s, research (e.g. Early Retirement Now's safe-withdrawal series) suggests 3% to 3.5% is more durable — which raises your target to roughly 28–33× expenses.
- Taxes and healthcare are easy to underestimate. Your "expenses" should include income taxes on withdrawals and health coverage. In the US, managing your Modified Adjusted Gross Income (MAGI) can unlock ACA subsidies — a real lever for early retirees.
- Fixed vs. flexible spending. If a chunk of your budget is discretionary, you can throttle it in down years, which makes a higher withdrawal rate safer than the static rule implies.
Related Tools
Decision guide
Turn a FIRE date into a planning range
A FIRE calculator connects spending, current investments, ongoing savings, and expected growth. Because every input can change, the most useful output is a range under conservative, base, and optimistic assumptions.
Your target equals spending divided by the selected rate.
Compare cautious, base, and stronger real-return cases.
What this model includes
- FI target and estimated time to reach it
- Portfolio, savings, return, and inflation assumptions
What to add outside the model
- Taxes, sequence risk, benefit timing, and one-off goals
- Income or spending changes unless entered
Calculation standard: Formula details, source policy, tests, and limitations are documented in the FinancialDepth methodology. Reviewed July 18, 2026.