3.5% vs 4% Withdrawal Rate: How They Compare

A 4% withdrawal rate means taking 4% of your starting portfolio in the first year of retirement and adjusting that dollar amount for inflation each year after; a 3.5% rate follows the same method but starts lower, which under the same assumptions produces less income today in exchange for a larger remaining balance and more room for the portfolio to absorb bad markets.

The "4% rule" is one of the most cited starting points in retirement and FIRE planning, and 3.5% is the number people reach for when they want a more cautious version of it. Neither is a guarantee, and neither is right for everyone. They are two different assumptions about how much of a portfolio to draw down each year.

This guide explains where the 4% figure came from, what each rate means mechanically, and what a lower rate does and does not buy, under a clearly stated set of assumptions rather than as advice about which to pick.

The short answer

Both rates describe the same basic system. You set a starting withdrawal as a percentage of your portfolio on the day you retire, you take that amount in year one, and in later years you adjust the dollar figure for inflation so your spending power stays roughly level. The only thing that changes between them is the starting percentage.

• The 4% rate starts by withdrawing 4% of the initial portfolio. On a larger base of withdrawals, it provides more income now.
• The 3.5% rate starts by withdrawing 3.5% of the initial portfolio. It provides less income now, and leaves a larger share of the portfolio invested.

The trade-off runs in both directions. A lower rate withdraws less, which under historical-style assumptions tends to leave more cushion against poor early returns and long retirements, but it also means either living on less income or needing a larger portfolio to fund the same lifestyle. A higher rate does the reverse. Which side of that trade-off fits depends on the retirement, the horizon, and the assumptions, none of which this article can decide for you.

Side-by-side comparison

Every row is a trade-off, not a verdict. A lower rate improves one thing (resilience under the stated assumptions) at the direct cost of another (income, or the portfolio size required). The table does not say which matters more for any given person.

Where the 4% rule came from

The 4% figure has a specific and factual origin worth knowing. In 1994, financial planner William Bengen studied historical US market returns and asked what fixed starting withdrawal rate, adjusted for inflation each year afterward, would have survived every rolling 30-year retirement period in his data. He found that a starting rate of around 4% held up across those historical periods.

A few years later, in 1998, three professors at Trinity University published a related study, widely known as the Trinity study, that examined portfolio survival across different stock and bond mixes and withdrawal rates over historical periods. Its results were popularly summarised as support for a roughly 4% starting withdrawal, and the shorthand "4% rule" stuck.

Two facts about that research matter for reading it correctly. First, it was based on historical US returns over specific past periods, which are not a promise about the future. Second, it tested a 30-year horizon with particular portfolio mixes and assumptions. Change the horizon, the asset mix, the fees, or the return environment, and the sustainable rate changes with them. Later analyses, including some 2020s refreshes, have proposed both higher and lower starting figures under different assumptions, which is exactly why a more cautious 3.5% is often discussed alongside the original 4%.

What each rate means plainly

Under both rates, the mechanics are identical apart from the starting percentage.

Year one: multiply the starting portfolio by the rate to get the first withdrawal. At 4% on $1,000,000 that is $40,000; at 3.5% it is $35,000.

Every year after: you do not recalculate the percentage against the new balance. Instead you take last year's dollar withdrawal and adjust it for Inflation, so your purchasing power stays roughly constant even as prices rise. This is why the rule is sometimes called an "inflation-adjusted" withdrawal strategy.

The lower rate is not a different system. It is the same rule with a smaller opening draw, which leaves proportionally more of the portfolio invested to keep compounding and to absorb the sequence of returns, especially poor returns early in retirement, that a drawdown is most sensitive to.

A worked example

Assume a $1,000,000 portfolio at the start of retirement. Under these assumptions, here is the first-year picture at each rate.

At 4%: the first-year withdrawal is 4% of $1,000,000, which is $40,000.

At 3.5%: the first-year withdrawal is 3.5% of $1,000,000, which is $35,000.

The difference is $5,000 of income in year one, roughly 12.5% less spending, and that gap then carries forward (both figures rise with inflation in later years, but the 3.5% path stays proportionally lower).

Now look at it from the other direction, from the portfolio side. Suppose you want $40,000 of first-year income. The portfolio each rate requires is:

To fund the same $40,000 at the more conservative 3.5% rate, the portfolio has to be about $142,857 larger, roughly 14% more, because you are drawing a smaller slice of it. That is the core of the trade-off stated numerically: a lower rate either means accepting less income from a given portfolio, or accumulating a larger portfolio to reach the same income. You can run your own portfolio size, withdrawal rate, and horizon in the Safe Withdrawal Rate Calculator to see how each choice plays out under your assumptions, and estimate the portfolio you would need to reach in the FIRE Calculator.

Which to use when

Neither rate is universally correct, and this article does not recommend one. What each rate does under a shared set of historical-style assumptions is reasonably clear, and that is what can inform a choice:

• A 4% starting rate provides more income now from a given portfolio, at the cost of a smaller invested buffer. Under the same assumptions it has less room to absorb a poor sequence of early returns or a retirement longer than the tested horizon.
• A 3.5% starting rate provides less income now and requires a larger portfolio for the same spending, in exchange for a bigger invested cushion and, under the same assumptions, more tolerance for weak early markets and longer horizons.
• The right assumptions vary by situation. A longer retirement, a more conservative return outlook, higher fees, or a wish for a larger safety margin all push the sustainable starting rate down; a shorter horizon or a willingness to adjust spending later can support a higher one.

The reliable habit is to treat any single percentage as a starting assumption to test, not a fixed guarantee, and to re-run it against your own horizon, portfolio mix, and spending flexibility. Historical survival across past periods is not a promise about future outcomes.