What Is the 4% Rule?
The 4% rule says you can withdraw 4% of your investment portfolio in your first year of retirement, then adjust that dollar amount for inflation each year, with a high historical probability your money lasts at least 30 years. It's the most widely cited rule of thumb in retirement planning — and the foundation of every FIRE number. Here's where it comes from, how it works, and where it breaks down.
Key takeaways
- Withdraw 4% in year one, then adjust that amount for inflation annually.
- It flips into a savings target: 4% withdrawal = 25× annual expenses.
- It came from the Trinity Study, based on a 30-year retirement.
- Early retirees often use 3.25%–3.5% for a longer horizon.
Where the 4% rule comes from
The rule traces back to 1990s research, most famously the Trinity Study, which tested how different withdrawal rates would have survived across decades of real U.S. market history. The finding: a retiree who withdrew 4% of a balanced stock-and-bond portfolio in the first year, then increased that dollar amount by inflation each year, almost never ran out of money over a 30-year retirement. It became shorthand for "how much can I safely spend?"
How it works in practice
Say you retire with $1,000,000. In year one you withdraw 4% — that's $40,000. If inflation is 3% the next year, you don't take 4% of the new balance; you take last year's $40,000 plus 3%, or about $41,200. You keep adjusting for inflation, not for market swings, so your spending power stays roughly constant.
The 4% rule flipped: your FIRE number
Run the math backwards and the rule becomes a savings target. If 4% of your portfolio must cover your annual expenses, then your portfolio needs to be 25 times those expenses (because 1 ÷ 0.04 = 25). Spend $40,000 a year? You need $1,000,000. This "25× expenses" figure is what the FIRE community calls your FIRE number.
The limits of the 4% rule
It's a guideline, not a guarantee. Three caveats matter, especially for FIRE:
- It assumed a 30-year retirement. Retire at 40 and you may need the money to last 50+ years, which argues for a lower rate.
- It ignores taxes and fees. Real withdrawals are reduced by both.
- Sequence-of-returns risk is real. A crash in your first few retirement years is far more damaging than the same crash later.
That's why many early retirees plan around 3.25%–3.5%, keep a cash buffer, or stay flexible with spending in down years.
Frequently asked questions
What is the 4% rule?
The 4% rule is a guideline that says you can withdraw 4% of your investment portfolio in your first year of retirement, then adjust that dollar amount for inflation each year, with a high historical probability the money lasts 30 or more years.
Where does the 4% rule come from?
It comes from the Trinity Study and related 1990s research, which tested historical U.S. market returns and found a 4% inflation-adjusted withdrawal rate rarely depleted a balanced portfolio over 30 years.
Is 4% safe for early retirement?
The 4% rule was based on a 30-year retirement. Early retirees planning for 40 to 50 years often use a more conservative 3.25% to 3.5% withdrawal rate to add a margin of safety.
Related: How to Calculate Your FIRE Number · How Much Do You Need to Retire Early? · FIRE Calculator