"If I spend 8,000 yuan a month in retirement, how much do I need to save?" Many people sense the answer but cannot compute it. Guessing "a couple of million" is not a plan — but the 4% rule turns it into a one-minute calculation. Today we explain this classic retirement rule, its underlying assumptions, and its limits, so you can turn a vague anxiety into a concrete number.
What Is the 4% Rule: Withdraw 4% a Year, Last 30 Years
The 4% rule comes from a 1994 study by William Bengen. Back-tested on US market data, if you withdraw 4% of your portfolio each year in retirement (rising with inflation), the money lasts at least 30 years. The core formula: required nest egg = first-year spending ÷ 4% — in other words, 25 times your annual spending.
Example: Xiao Liu plans to spend 8,000 yuan a month in retirement, or 96,000 yuan a year. By the 4% rule he needs 96,000 ÷ 0.04 = 2.4 million yuan. If he plans to spend 12,000 yuan a month (144,000 a year), he needs 3.6 million. There is a neat mental shortcut: monthly spending × 300 = required nest egg (because 96,000 ÷ 0.04 = 2.4 million, and 2.4 million ÷ 8,000 = 300).
This "300 times monthly spending" shortcut is practical: spend 10,000 a month → save 3 million; spend 20,000 a month → save 6 million. To compute annual withdrawals and the exact planning horizon, use our retirement calculator — enter your target and expected withdrawal years to work backward to what you need to save each month.
| Monthly Retirement Spending | Annual Spending | Nest Egg at 4% | Shortcut (monthly × 300) |
|---|---|---|---|
| 5,000 yuan | 60,000 | 1.5 million | 1.5 million |
| 8,000 yuan | 96,000 | 2.4 million | 2.4 million |
| 10,000 yuan | 120,000 | 3 million | 3 million |
| 15,000 yuan | 180,000 | 4.5 million | 4.5 million |
| 20,000 yuan | 240,000 | 6 million | 6 million |
Note the premise: the 4% rule assumes your money keeps earning returns (the historical back-test assumed a stock-and-bond portfolio earning roughly 7% a year, enough to preserve purchasing power after inflation) — not that it sits in a current account while you draw it down. A large part of your retirement portfolio should be in assets that grow over the long term.
Withdrawal Rates Are Not Fixed: 3% Is Safer, 5% Is Riskier
Four percent is the historical "safe" number, but you can adjust it to your risk tolerance. The lower the withdrawal rate, the safer your principal — but the more you need to save. A 3% rate → 33.3 times annual spending; a 5% rate → 20 times annual spending, but with a clearly higher risk of running dry.
Using the formula: required nest egg = annual spending ÷ withdrawal rate. At 8,000 yuan a month (96,000 a year): a 3% rate needs 3.2 million; 4% needs 2.4 million; 5% needs 1.92 million. The three tiers differ by 1.28 million — that is the price of safety margin. Younger or stronger investors may accept 4%-5%; those who need certainty and cannot stomach a big drawdown should choose 3%.
Another often-missed variable is the length of retirement. Retiring at 50 versus 65 changes the number of years your money must last by 15 — and the same spending level needs a very different nest egg. The earlier you retire, the longer the support period and the lower your safe withdrawal rate. This is why the 4% rule is anchored on a 30-year horizon: stretch it to 40 years and the safe rate drops to roughly 3.5%.
To model your portfolio over time, use our CAGR calculator with your annual return and yearly withdrawal to see what remains after 10, 20, and 30 years; then pair it with the compound interest calculator to project how today's savings grow before retirement and work backward to your monthly contribution.
Do Not Ignore These Two: Inflation and Your State Pension
The 4% rule numbers look intimidating (spend 10,000 a month → save 3 million), but two variables change the conclusion.
First, your state pension is also income. In most countries, employees have a basic pension in retirement, typically providing the equivalent of a few thousand yuan a month. This money "covers" part of your retirement spending. If you spend 8,000 a month and receive 3,000 in pension, the 4% rule only needs to cover the remaining 5,000 — a nest egg of 1.5 million instead of 2.4 million. Calculate your expected pension first, then the gap, and the number becomes far more realistic.
Second, inflation erodes purchasing power. The 4% rule already assumes withdrawals rise with inflation each year, so it works in today's purchasing-power terms. If future inflation runs higher than history, scale your target up accordingly. Use "today's prices" as your spending baseline and avoid stacking inflation anxiety on top of the rule, which distorts the target.
To turn this into action: use the retirement calculator to estimate how much your pension covers, work backward to your personal savings gap, then use the CAGR and compound-interest calculators to figure out "how much to save each month." Vague retirement anxiety becomes an executable saving plan.
FAQ
Q1: Does the 4% rule apply outside the US?
The principle applies, but discount the number. The 4% figure comes from back-testing US stock and bond markets. In markets with higher volatility and different long-run returns, a safer assumption is 3%-3.5%. The core logic — funding long-term withdrawals with investment returns — holds in every market.
Q2: Should my home count toward the retirement nest egg?
Your primary home is usually not part of the "withdrawable" nest egg, because you cannot sell it to pay for groceries. But if you plan to downsize and use the difference to fund retirement, that cash flow can be added as extra income. The 4% rule applies to investable, withdrawable financial assets.
Q3: Can social security fully cover retirement spending?
For most people, no. Pension replacement rates (pension ÷ pre-retirement salary) are often around 40%-50%, meaning retirement income may be less than half of working income. That is precisely why personal savings and the 4% rule exist — to fill the gap beyond the pension.
Q4: Will withdrawing 4% ever drain the principal?
In historical back-tests the portfolio usually still has a balance after 30 years, but if the market crashes early in retirement (a "sequence-of-returns risk"), withdrawing 4% can accelerate the drain. It is a probability, not a guarantee — which is why conservative retirees choose 3%, withdraw in tranches, and keep one or two years of cash buffer.
Q5: When should I start planning with the 4% rule?
The earlier, the better. Starting at 40 versus 55 makes an enormous difference thanks to compounding. Early planning keeps monthly pressure low: for a 2.4-million target at 5% annual, starting at 40 needs about 2,900 yuan a month, while starting at 55 needs about 16,000 a month. Stretch the timeline in a compound-interest calculator and you will see that "starting early" beats "saving more."