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
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.