How much do you need to retire? Strip away the calculators and you land on a shockingly simple number: 25 times your annual spending. The famous 4% rule says you can withdraw 4% of your portfolio in year one and ride it for 30 years. But the rule hides a risk most people never see: what decides whether you go broke isn't your average return — it's the order the returns arrive in.
What the 4% Rule Says
Withdraw 4% of your portfolio in year one, then increase that dollar amount every year with inflation. So $1,000,000 pays you $40,000 in year one, roughly $41,200 the next year (at 3% inflation), and so on for three decades. The rule comes from William Bengen's 1994 research and the later Trinity Study, both of which backtested withdrawal rates against US stock-and-bond history.
The 25× Shortcut
4% is the reciprocal of 25, so the whole rule collapses to one multiplication:
Nest egg = annual spending × 25
Spend $40,000 a year? You need about $1,000,000. Spend $60,000? $1,500,000. Spend $100,000? $2,500,000. The number feels enormous because it is — but that's the honest size of a 30-year cushion.
Want a longer or safer cushion? The math scales cleanly: a 3.5% withdrawal rate means 28.6× your spending, and 3% means 33×. Retiring at 45 instead of 65 forces the lower rate, because the money has to last longer.
Where 4% Came From
Crucial context: 4% isn't the average result — it's the worst-case-to-survive result. Bengen tested 30-year windows across US history and picked the withdrawal rate that survived even the ugliest one: retiring in 1966, just before the 1970s inflation spike and a long, flat market. Recognize what that means — 4% is a floor derived from the harshest stretch of American market history, not a target calibrated to a friendly one.
The Risk No One Talks About: Sequence
Now the part that should reframe how you think about retirement. Two retirees each have $1,000,000, each withdraw $40,000 a year, and each experience the exact same average return of 6.6%. The only difference is when the bad years land.
- Retiree A retires into a crash — five losing years of −15% come first, then twenty good years of +12%. Same 6.6% average. A runs out of money in year 22.
- Retiree B retires into a boom — the twenty +12% years come first, then the five −15% years. B ends the 25 years with $2,721,760.
Identical average return, identical withdrawals. One ends broke, the other is a multi-millionaire. That gap is sequence-of-returns risk — and it's why "average return" is a nearly useless number for anyone actually withdrawing money.
Why the First Five Years Decide Everything
The mechanism is what makes it so dangerous: when you're withdrawing, an early loss isn't just a paper loss. You sell shares at the bottom to fund living expenses, locking in the damage permanently, and the portfolio never recovers to its old size. A flat or down first five years is the single biggest hazard a retiree faces. This is the logic behind "bond tents" and target-date funds that turn conservative right around the retirement date.
How to Actually Use the Rule
1. Compute your number
Annual spending × 25. One multiplication, no spreadsheet required.
2. Split "must" from "nice" spending
Cutting your ongoing spending by $10,000 a year shrinks the nest egg you need by $250,000. Spending is the lever most people skip.
3. Stress-test the first five years
The danger zone is years one through five, not year twenty. Plan around the possibility of retiring into a down market.
4. Treat 4% as a target, not a promise
Build in a buffer, or plan to trim withdrawals in a bad first year. Flexibility is cheap; running out is not.
5. Keep the growth engine running
The rule assumes a sensible stock-and-bond mix, not cash. A portfolio left in low-yield cash quietly changes the math.
When 4% Breaks Down
Four caveats:
- It's a backtest of US history. Japan and several other markets would have supported far less. The future is not obligated to repeat 1966.
- 4% was built for ~30 years. Earlier retirement calls for 3.5% or 3%, which means a 29×–33× nest egg instead of 25×.
- It ignores fees and taxes. A 1% advisory fee is a full quarter of your 4% — it has to come out of your spending or your growth.
- "Success" is a low bar. The rule survives if you don't hit $0 in 30 years. It does not promise you keep your principal or leave an inheritance.
Try It Yourself
Find your number: total up the spending you couldn't cut, multiply by 25, and that's the nest-egg target. Then see how long it'll actually take to get there — plug a monthly contribution and a growth rate into the Savings Goal Calculator. The distance from today to your 25× number is, quite literally, how much work you have left.