How Much Do You Need to Retire

The most anxiety-inducing question in personal finance is "how much do I need to retire?" Surveys show wildly unrealistic answers — some people say $500,000, others say $10 million. Both could be right or wrong depending on one variable: how much you spend per year. Your retirement number isn't determined by your income, your job title, or what your neighbor has. It's determined by your annual expenses multiplied by a factor that ensures your money outlasts you. The most widely used formula is simple: multiply your annual expenses by 25. If you spend $60,000 per year, you need $1.5 million. If you spend $40,000, you need $1 million. If you spend $100,000, you need $2.5 million. That's your number.

The Math Behind Your Retirement Number

The 25x rule is derived from the 4% rule, developed by financial planner William Bengen in 1994. Bengen studied every 30-year retirement period in U.S. market history going back to 1926 and asked: what's the maximum percentage of a balanced portfolio you could withdraw in year one, adjusting for inflation each year, and never run out of money? The answer: approximately 4%.

If you have $1.5 million and withdraw 4% in year one, you take out $60,000. Each subsequent year, you increase that withdrawal by inflation. In 96% of the historical periods Bengen studied, the portfolio lasted at least 30 years. In many cases, the retiree died with more money than they started with because market returns exceeded withdrawals.

The 25x multiplier is simply the inverse of 4% (1 / 0.04 = 25). It tells you how large your portfolio needs to be relative to your annual spending to sustain indefinite withdrawals.

Several factors affect whether 25x is enough for you. If you're retiring before 60, you may need a longer runway than 30 years. Consider using 28-33x instead (a 3-3.5% withdrawal rate). If you have pension income or Social Security, subtract that from your expenses before calculating. If you spend $60,000 per year and Social Security covers $24,000, you only need your portfolio to cover $36,000 — so your number is $900,000 (25 x $36,000), not $1.5 million. If you're flexible on spending, you can use a higher withdrawal rate because you can cut back during market downturns.

Why It Matters for Investors

Having a specific retirement number transforms retirement from an abstract anxiety into a concrete goal. Instead of vaguely worrying about "having enough," you can measure your progress toward a definitive target. If your number is $1.5 million and you currently have $400,000, you know exactly where you stand and can calculate what you need to save monthly to close the gap.

Your retirement number also reveals whether your current savings rate is sufficient. If you need $1.5 million by age 65 and you're 35 with $100,000 invested, you need to save approximately $800 per month at a 10% return to reach your goal. If you're only saving $400 per month, you either need to save more, work longer, or plan to spend less in retirement. Knowing the number lets you make informed trade-offs.

The number also highlights the most powerful lever you have: spending. Reducing your annual expenses by just $10,000 per year lowers your retirement number by $250,000. A lifestyle slightly more modest than your peers can mean retiring five to ten years earlier. This is why the FIRE community obsesses over spending — it's the variable that matters most.

Real Example

Consider a couple, both 40 years old, currently spending $80,000 per year. Their retirement number is $2 million (25 x $80,000). They currently have $300,000 invested. At a 10% average return with no additional contributions, their $300,000 would grow to approximately $1.3 million by age 65 — short of their goal by $700,000. They need to save approximately $850 per month to close the gap. Now consider the same couple who reduces their spending to $65,000 per year. Their new retirement number is $1,625,000. Their existing portfolio growth covers $1.3 million, and they only need to save about $500 per month to close the smaller gap. Or they could retire three years earlier. One lifestyle adjustment — $15,000 per year less in spending — changed their entire retirement trajectory more than any investment strategy ever could.