The 4% rule and safe withdrawal rate, explained

What is a safe withdrawal rate?

Your safe withdrawal rate is the percentage of your starting portfolio you can spend in your first year of retirement — then keep spending, adjusted for inflation — with a high probability of the money lasting your whole retirement. The "4% rule" is just the most famous safe withdrawal rate: withdraw 4% year one, raise that dollar figure with inflation each year after, and history says a stock-heavy portfolio usually survives ~30 years.

The withdrawal rate is the hinge your entire FI number swings on:

FI number = annual spending ÷ safe withdrawal rate

At 4%, that's spending × 25. Spend $50,000 a year and your FI number is $1,250,000. Choose a more cautious 3.5% and the same spending needs $1,428,571. Same life, same budget — a different assumption about a single percentage, and the target moves by ~$180,000. That is exactly why a withdrawal rate you can't see or check is a withdrawal rate you can't trust. (For the full FI-number formula and the 25x framing, see what is your FI number.)

Where the 4% rule comes from (Bengen 1994)

The 4% rule isn't a rule of thumb someone guessed — it comes from a 1994 study of real US market history. Financial planner William Bengen published "Determining Withdrawal Rates Using Historical Data" in the Journal of Financial Planning in October 1994. He modeled a retiree drawing an inflation-adjusted income from a mix of the S&P 500 and intermediate-term US Treasuries, and tested every historical retirement start date he had data for — including people who retired straight into the 1929 crash, the 1930s, and 1970s stagflation.

His finding: at a 4% initial withdrawal rate, adjusted for inflation each year, no historical portfolio he examined ran dry in less than about 33 years. Two details usually get lost:

• 33 years was the worst case, not the typical one. In most historical periods the same 4% withdrawal left the portfolio lasting 50 years or longer. 4% was calibrated to survive the single worst start date in the data.
• It depended on owning a lot of stocks. Bengen advised a stock allocation "as close to 75 percent as possible, and in no cases less than 50 percent." The 4% number falls apart with a bond-heavy portfolio.

Bengen later named this maximum-historical-survivor rate the SAFEMAX. Worth knowing: he has revised his own headline number several times as he added asset classes and data — to 4.5% (or 4.1% for a taxable account) in his 2006 book, and as high as ~4.7% more recently. When the author of the 4% rule keeps moving his own number, that's your signal it's a research estimate under active debate, not a constant of nature.

The 4% rule vs. the Trinity study — same era, different question

People use "the 4% rule" and "the Trinity study" interchangeably, but they're two separate pieces of research that happen to agree. Bengen asked: what's the highest rate that survived even the worst historical start date? The Trinity study — three Trinity University finance professors, Cooley, Hubbard, and Walz, first published in 1998 and updated in 2011 — asked a probability question instead: across all historical periods, what fraction succeeded?

The Trinity headline most people cite: a 4% inflation-adjusted withdrawal over a 30-year retirement from a 50/50 stock/bond portfolio succeeded in about 96% of historical periods. Same 4%, same ~30-year frame — approached from the other direction. Both are built on US historical data and a roughly 30-year retirement, and that shared fine print is the whole ballgame for anyone retiring early.

Is the 4% rule still safe in 2026?

As a ~30-year planning baseline, yes — with caveats, and with some current research arguing for a slightly lower starting point. The 4% rule was never a promise; it's the worst historical outcome dressed up as a round number, and today's starting conditions aren't identical to history's.

The clearest recent counterweight is Morningstar's annual retirement-income research. For 2026, Morningstar puts the safe starting withdrawal rate at about 3.9% for a retiree who wants fixed, inflation-adjusted spending — assuming a 30-year horizon, a 90% success probability, and a 30–50% equity allocation. Their reasoning is forward-looking: higher stock valuations and bond yields than the historical average imply somewhat lower future returns, so they trim the starting rate. (Notably, Morningstar also shows that a retiree willing to flex spending in bad years can start closer to 5.7% — more on flexibility below.)

So the honest 2026 read: 4% is a reasonable 30-year anchor, ~3.9% is a defensible slightly-more-cautious version of the same idea, and the exact right number is an assumption you should set on purpose — not a default you inherit without noticing. The point isn't which guru's number is "correct." It's that you can see the number, change it, and watch what it does to your plan.

The 4% rule and early retirement (FIRE): why 3.25–3.5%

If your retirement could last 40, 50, or 60 years instead of 30, the 4% rule gets materially less safe, and the commonly used conservative adjustment is a starting rate of 3.25–3.5%. This is the single most important caveat for the FIRE crowd, because retiring at 40 means betting a 50-year outcome on 30-year evidence.

The most-cited public work on long horizons is the Safe Withdrawal Rate series by Karsten Jeske ("Big ERN") at Early Retirement Now, which re-ran the historical simulations for early-retirement lengths. Two findings worth carrying around:

• A 4% withdrawal that succeeded in about 95% of 30-year historical periods (50/50 portfolio) succeeded in only about 65% of 60-year periods. In his words, the failure probability is roughly 7 times higher over 60 years than over 30.
• Starting rates in the 3.25–3.5% range survived even the most catastrophic historical start dates in his analysis — which is why his shorthand is "3.5% is the new 4%."
• A 5% starting rate had an unacceptably low success rate even at 30 years, and far worse over 60.

That's why FIManager's calculator ships with a one-tap 3.5% long-horizon preset next to the 4% default, and lets you set anything from 3% to 5%. Neither 4% nor 3.5% is "the answer" — they're different assumptions for different retirement lengths, and your FI number moves a lot between them.

Safe withdrawal rate by retirement length (the table)

Here's the mapping, with each row's basis cited so you can check it. The withdrawal rate you pick determines the multiple of spending you need — and therefore your FI number.

And here's what those rates do to a real target, using the calculator's exact spending ÷ SWR math at two example budgets:

This second table is pure arithmetic — annual spend ÷ rate — and it's yours to check with a calculator in ten seconds. No hidden assumptions.

Worked example — what the withdrawal rate costs you in years

The rate doesn't just change your target; it changes when you hit it. All figures below use the calculator's exact closed-form math and are estimates in today's (real) dollars, not predictions.

Inputs: age 40 · $60,000/yr spending · $250,000 invested · $35,000/yr contributions · 5% real return.

The safety margin costs about $214,000 more saved and roughly 1.9 extra years of work. That's the real 4%-vs-3.5% trade-off — and it's a decision worth making with both numbers in front of you, not one you inherit by default.

Run your own: fimanager.app/fi-calculator — set the withdrawal rate slider anywhere from 3% to 5% and watch your FI number and FI date move. Assumptions stay on screen.

Can you withdraw more than 4%? (flexibility and guardrails)

Sometimes — if you're willing to spend flexibly instead of on autopilot. Every "safe withdrawal rate" above assumes you set a starting income, inflation-adjust it every year, and never cut back even in a crash. That rigid assumption is what forces the rate down. Retirees who reduce spending in bad market years — "guardrail" strategies — can historically start higher; Morningstar's 2026 work shows a flexible-spending retiree starting near 5.7% versus 3.9% for fixed spending.

The catch is that flexibility only helps if you can actually tolerate a real spending cut when markets fall — the exact moment it's hardest. It's a genuine lever, not a free lunch, and it's a personal-tolerance question no rule can answer for you.

What the 4% rule quietly leaves out

The 4% rule is a useful anchor, but treating it as the finish line hides three things it was never built to handle:

• Sequence-of-returns risk. The rule assumes you survive the average, but a crash in your first few retirement years does far more damage than the same crash later — two retirees with identical average returns can end up in completely different places. A single withdrawal rate can't see this. (Deep dive: sequence-of-returns risk.)
• Taxes. Withdrawals from pre-tax accounts are taxable income; 4% gross and 4% spendable aren't the same number. Your spending estimate has to include the taxes you'll still owe.
• A single answer instead of a probability. "You need $1.25M" sounds precise. "Your plan has an 88% chance of success across thousands of market histories" is honest. The upgrade from a fixed withdrawal rate to a chance of success is the whole reason Monte Carlo simulation exists. (That illustrative 88% is an example, not a product stat.)

That's the difference between a rule of thumb and a plan. FIManager runs the chance-of-success simulation with every assumption — return, volatility, iteration count, per-year cash flow — visible and editable, because a projection you can't inspect is one you can't trust.

FAQ

What is the 4% rule?

The 4% rule says you can withdraw 4% of your investment portfolio in your first year of retirement, increase that dollar amount for inflation each year, and have a high chance of the money lasting about 30 years. It comes from William Bengen's 1994 research on US market history. Withdrawing 4% means you need 25 times your annual spending.

What is a safe withdrawal rate?

A safe withdrawal rate (SWR) is the percentage of your starting portfolio you can spend in year one — then keep spending, inflation-adjusted — with a high probability of not running out over your retirement. The 4% rule is simply the best-known safe withdrawal rate; "4% rule" and "safe withdrawal rate" describe the same idea.

Is the 4% rule still safe in 2026?

As a ~30-year baseline it remains reasonable and is grounded in Bengen (1994) and the Trinity study (~96% historical success). Some current research is more cautious: Morningstar's 2026 analysis suggests a ~3.9% starting rate for fixed inflation-adjusted spending given today's valuations. And for early retirements of 40+ years, historical simulations show 4% failing far more often. Treat it as a starting assumption to stress-test, not a guarantee.

Where does the 4% rule come from?

Financial planner William Bengen, in "Determining Withdrawal Rates Using Historical Data" (Journal of Financial Planning, October 1994). He found that a 4% inflation-adjusted withdrawal from a stock-heavy portfolio survived at least ~33 years across every historical start date he tested — the worst case, not the typical one. The Trinity study (Cooley, Hubbard, and Walz, 1998, updated 2011) reached a compatible conclusion from a probability angle.

Does the 4% rule work for early retirement (FIRE)?

Less well. Bengen and Trinity studied ~30-year retirements; a 40–60-year retirement stretches the math past its data. Early Retirement Now's historical simulations show 4% success dropping from about 95% over 30 years to about 65% over 60 years, which is why many early retirees plan at 3.25–3.5% instead.

What safe withdrawal rate should I use for a 50-year retirement?

For very long horizons, researchers commonly cite the 3.25–3.5% range, which survived even the worst historical start dates in Early Retirement Now's analysis. At 3.5% you need about 28.6x your annual spending; at 3.25%, about 30.8x. The right choice depends on your risk tolerance and how flexible your spending can be — set it deliberately and see the impact.

Is 3.5% "the new 4%"?

That's the shorthand from Early Retirement Now for early retirees: for a 50–60-year horizon, a 3.5% starting rate historically held up where 4% sometimes didn't. It's not a replacement law — it's the more cautious assumption appropriate to a much longer retirement. Compute both and know which one you're planning against.

Can I withdraw more than 4%?

Potentially, if you'll spend flexibly. The standard rates assume rigid inflation-adjusted spending you never cut. Retirees who reduce spending in down markets ("guardrails") can historically start higher — Morningstar's 2026 work shows a flexible spender starting near 5.7% versus 3.9% for fixed spending. The trade-off is that you must actually accept a spending cut when markets fall.

Does the 4% rule account for taxes?

No. The 4% is a gross withdrawal; taxes on withdrawals from pre-tax accounts come out of that. Build the taxes you'll still owe into your annual spending estimate rather than assuming 4% is all spendable.