How Much Money Do You Need to Retire?

Start With Spending, Not Income

Almost everyone begins this calculation with their salary. That is the wrong input.

What you need to fund in retirement is your spending, and the two are rarely equal. Retirement typically removes commuting costs, work clothes, the mortgage if it is paid off by then, and whatever you were saving for retirement itself. It adds healthcare, and often more travel in the early years.

A common planning shortcut puts retirement spending at 70% to 80% of pre-retirement income. Treat that as a placeholder until you have looked at your actual outgoings, because the shortcut hides enormous variation. Someone who owns their home outright and someone still paying rent have very different numbers at the same salary.

Work out what a year of your retired life costs, in today’s money. Everything else in this article scales off that figure.

The 25x Rule and Where It Came From

The 4% figure traces to William Bengen, who published research in 1994 testing how much a retiree could withdraw each year without running out of money. Using US market data going back to 1926, he found that withdrawing 4% of the starting portfolio, then adjusting that amount for inflation annually, survived every 30-year period in the record. The Trinity Study reinforced the finding in 1998 using similar data.

So the rule has genuine research behind it. It also has three specific boundaries that get dropped whenever it is repeated: it was calibrated on US markets, over a 30-year retirement, with a portfolio of stocks and bonds held throughout.

Worked Example

Situation: You expect to spend 40,000 a year in retirement, in today’s money. These figures work in any currency.

The spending figure never changed. Only the assumed withdrawal rate did, and the target moved by two thirds.

Then subtract guaranteed income. If a state pension or annuity will cover 12,000 a year, your portfolio only needs to fund the remaining 28,000. At 4% that drops the target from 1,000,000 to 700,000, which is a larger single improvement than most people achieve by saving harder.

The Number That Changes Everything

Given how much the rate drives the answer, it deserves more scrutiny than it usually gets.

Wade Pfau applied Bengen’s methodology to the domestic market histories of 14 developed countries. The 4% withdrawal rate proved safe in only four of them. Countries whose twentieth-century markets included war, hyperinflation, or prolonged stagnation produced materially lower safe rates, and Pfau estimated a safe rate of 2.4% in 2020 conditions.

This matters directly if you are not investing in US markets, or if you are retiring somewhere the currency and market history look nothing like the American record. The 4% rule is not a law of finance. It is a description of what happened in one country’s unusually successful century.

Two further adjustments are worth knowing. Retiring early lengthens the horizon well beyond the 30 years Bengen tested, which argues for a lower rate. And sequence-of-returns risk means a market crash in your first few retired years does far more damage than the same crash a decade later, because you are selling assets to live on while they are cheap.

My own read: 4% is a reasonable planning anchor if you are invested in global equities with a roughly 30-year horizon, and 3% to 3.5% is the more defensible figure for early retirement or a single-country portfolio. Flexibility helps more than precision. Retirees who can cut spending in bad years survive scenarios that break rigid withdrawal schedules.

Working Out What to Save Each Month

Having a target is only half the job. The other half is the monthly figure that reaches it.

This is compound growth running forward, and the variable doing most of the work is time rather than the amount. Someone starting at 25 with a 40-year horizon needs to contribute far less each month than someone starting at 45 with 20 years, because the early contributions spend decades compounding. Our guide on how compound interest works covers the mechanics.

Two adjustments make the projection honest. Use a real return, meaning your expected return minus expected inflation, so the answer stays in today’s money and matches the spending figure you started with. And build in contribution increases, since saving a fixed percentage of a rising salary produces a very different result from saving a fixed amount for 30 years.

What the Simple Model Ignores

• Inflation over decades. At 3% annual inflation, today’s 40,000 of spending needs roughly 72,000 of nominal income in 20 years.
• Tax on withdrawals, which varies enormously by country and account type and can consume a meaningful share of what you draw.
• Healthcare costs, which tend to rise with age and are the single largest source of unplanned retirement spending in countries without comprehensive public cover.
• Longevity. Planning for 30 years is standard, but a couple retiring at 60 has a reasonable chance of one partner living past 90.
• Investment fees. A 1% annual fee compounds against you exactly as returns compound for you, and over 30 years it can consume a large fraction of the final balance.
• Property. A home you own reduces required spending; a home you plan to sell is a lump sum with timing risk attached.

If the Number Looks Impossible

For most people running this calculation for the first time, it does. That reaction is normal and the target is more movable than it appears.

Reducing planned spending is the most powerful lever, because it works twice: every 1,000 you cut from annual spending removes 25,000 from the target while also freeing money to save today. Working two or three years longer is the second most powerful, since it adds contributions, adds growth, and shortens the horizon the portfolio must cover.

Beyond that: check what guaranteed income you are already entitled to, since state pensions are frequently overlooked and directly reduce what the portfolio must produce. Reduce investment fees. Consider part-time work in early retirement, which cushions exactly the sequence-of-returns risk that does the most damage.

What does not help is abandoning the calculation because the answer is uncomfortable. A partial plan started today outperforms a perfect plan started in five years, and the arithmetic of compounding is unforgiving about delay in a way it is forgiving about amount.

Frequently Asked Questions

Is the 4% rule still valid?

As a rough planning anchor for a 30-year retirement in globally diversified markets, it remains reasonable. As a universal guarantee it never was. It came from US data over a specific period, and international testing found it safe in only 4 of 14 developed countries. Many planners now use 3% to 3.5% for longer horizons.

How much do I need to retire at 40?

Considerably more than the 25x rule suggests, because you may be funding 50 years rather than 30. Early retirees commonly plan at 3% or lower, which means 33 times annual spending or more, and often keep some earning capacity in reserve for the first decade.

Should I use gross income or spending to set the target?

Spending. Income includes tax, retirement contributions, and work-related costs that mostly disappear when you stop working. Building a target from income routinely overstates what you need by a wide margin.

Does the state pension count toward my target?

Yes, and it should be subtracted from the income your portfolio must generate rather than added to your savings target. Guaranteed income is worth a large multiple of itself: 12,000 a year of pension replaces roughly 300,000 of portfolio at a 4% withdrawal rate.

What return should I assume?

Use a real return, after inflation, and be conservative. Historical global equity returns have run around 5% to 7% real over long periods, with bonds lower. Assuming 8% or 10% real because recent years were strong is the most common way these projections mislead.

What is sequence-of-returns risk?

The risk that poor market returns arrive early in retirement rather than late. Two retirees can experience identical average returns over 30 years and end in completely different positions depending on the order, because withdrawals during a downturn permanently remove shares that would have recovered. It is the main argument for flexible spending.

Is my house part of my retirement fund?

Only if you intend to sell it or borrow against it. A home you live in reduces your spending rather than generating income, which lowers the target without contributing to the portfolio. Counting its full value as retirement savings while also planning to live in it counts the same asset twice.

The Bottom Line

Work out what a year of retirement costs, subtract any guaranteed income, and divide the remainder by your chosen withdrawal rate. The rate is where the judgement lives: 4% is a defensible anchor for a 30-year horizon in diversified markets, and 3% to 3.5% is more appropriate for early retirement or a concentrated single-country portfolio. Whatever number comes out, remember that cutting planned spending moves it faster than saving harder does. Run your own projection through the retirement calculator and test it at more than one return assumption, because a plan that only works at 8% is not really a plan.

Sources and Further Reading

• Bengen WP. “Determining Withdrawal Rates Using Historical Data.” Journal of Financial Planning, 1994.
• Cooley PL, Hubbard CM, Walz DT. “Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable” (the Trinity Study), 1998.
• Pfau WD – international research applying the Bengen methodology across 14 developed countries.
• OECD – Pensions at a Glance, for country-level retirement income systems.