The 4% Rule, Explained
Updated ·3 min read·Reviewed by the StockTools.ai Research Team
- ▸The 4% rule: withdraw 4% of your starting portfolio in year one, then raise that dollar amount with inflation each year after.
- ▸It came from studies of actual US market history, where a 30-year retirement usually survived — "usually" is doing a lot of work.
- ▸The order of returns matters more than the average: a crash in your first few retirement years is the real danger (sequence risk).
- ▸Your true safe rate depends on your time horizon, asset mix, and how much failure risk you will accept — it is rarely exactly 4%.
What the 4% rule actually says
The 4% rule is a starting-point answer to one of retirement’s hardest questions: how much can I spend each year without running out of money? It says take 4% of your portfolio in your first year of retirement, then increase that dollar figure with inflation every year after — regardless of what the market does. On a $1,000,000 portfolio that is $40,000 in year one, then about $41,200 the next year at 3% inflation, and so on.
The key detail people miss: after year one, you are not withdrawing 4% of the current balance. You are withdrawing a fixed, inflation-growing dollar amount. In a bad year that can mean pulling a much larger percentage of a shrunken portfolio — which is exactly where the rule gets dangerous.
Test your own withdrawal rate
Each simulated year draws a return from your mean and volatility, applies it to the balance, then subtracts that year's withdrawal — $40Kin year 1, increased with inflation every year after (the standard "4% rule" definition), never reduced back down if markets fall. Reproducible seed: 42.
Why this may look lower than the famous "4% rule":that figure comes from studies that replay actual historical decades, which have some mean-reversion baked in. This tool draws each year's return independently at random, which has no memory of the year before — a stricter, more conservative test that can show a lower safe rate for the same assumptions. Neither is more "correct"; they answer slightly different questions. Educational only, not financial advice.
Where it came from
The rule traces to 1990s research — financial planner William Bengen and later the Trinity study — that looked at whether a retiree could have survived every historical 30-year window using US stock and bond returns. Across those actual historical sequences, a roughly 4% inflation-adjusted withdrawal almost always lasted the full 30 years, even through the Depression and the 1970s.
That history-based method has one feature worth understanding: real market history contains some mean-reversion — bad stretches were often followed by recoveries. A simulation that draws each year’s return independently at random has no such memory, and tends to suggest a more conservative safe rate for the same assumptions. Neither is "wrong"; they answer slightly different questions.
Why it can fail: sequence-of-returns risk
Two retirees can earn the exact same average return over 30 years and end up in completely different places — one comfortable, one broke — purely because of when the good and bad years arrived. A steep decline in the first few years of retirement, while you are also withdrawing, permanently shrinks the base your portfolio has to recover from. The same decline ten years later does far less damage.
This is sequence-of-returns risk, and it is why the 4% rule is a guideline rather than a guarantee. It is also why flexibility helps so much: trimming spending in down years, keeping a cash buffer, or using a guardrails strategy can rescue plans that a rigid 4% would sink.
Finding your own number
Your safe withdrawal rate is not a universal constant — it moves with your retirement length, your stock/bond mix, and how much risk of running out you are willing to tolerate. A 40-year early retirement needs a lower rate than a 25-year one. A more volatile portfolio needs a lower rate for the same confidence.
The calculator above runs thousands of randomized retirements from your own assumptions — a Monte Carlo simulation. Use "test a rate" to see the probability a given withdrawal rate lasts, or "find my safe rate" to solve for the highest rate that clears a success bar you choose. Treat the output as a way to reason about ranges and sequence risk — not a promise about your specific future.
FAQ
Is the 4% rule still valid?
It remains a reasonable starting point, but it was never a law. It assumes a ~30-year horizon and a stock-heavy portfolio, and it can fail if a severe downturn hits early in retirement. Longer retirements or more conservative portfolios often call for a lower rate; the right move is to test your own numbers rather than assume 4% fits.
What is a safe withdrawal rate?
The highest percentage you can withdraw and still have your money last, at an acceptable probability of success — often 90% or 95% of simulated retirements never running out. It depends on your horizon, asset mix, and risk tolerance, so it is a range, not a single fixed number.
Does the 4% include taxes?
No. The 4% is a gross withdrawal from the portfolio; taxes come out of that amount, and they depend on your account types (taxable, traditional, Roth). Plan your spending on an after-tax basis, which effectively lowers how much of the withdrawal you can actually spend.
What if the market crashes right after I retire?
That is the worst-case scenario the rule is most vulnerable to — sequence-of-returns risk. Defenses include holding a cash or bond buffer to avoid selling stocks at the bottom, cutting discretionary spending in down years, or using a flexible "guardrails" withdrawal strategy instead of a rigid inflation-adjusted amount.
Put it to work
Related guides
Sources & further reading
- ▸ Bengen, W. (1994). Determining Withdrawal Rates Using Historical Data. Journal of Financial Planning.
- ▸ Cooley, Hubbard & Walz (1998). Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable ("The Trinity Study"). AAII Journal.
More to learn
Educational only — not financial advice. Concepts simplified for clarity; markets are messier than definitions.