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Lifecycle

Your Retirement Number

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Your Retirement Number

Before you can reach a destination, you must know where you're going. Retirement planning is no different. Your retirement number is the single most important figure in your financial life—the lump sum of investment capital you must accumulate to support yourself without employment income for the rest of your life. It transforms retirement from an abstract dream ("I'll retire someday") into a concrete, measurable milestone with a clear path forward.

Yet calculating this number is deceptively simple on the surface and complex in the details. The fundamental question is straightforward: How much money do you need to retire? But answering it requires you to make assumptions about your spending, your investment returns, inflation, healthcare costs, longevity, and a dozen other variables that will evolve over your lifetime. This chapter guides you through that process, from simple rules of thumb to sophisticated projections, so you understand not just what your number is, but why it matters and how to refine it as your life unfolds.

From annual expenses to a lump sum​

Your retirement number begins with a simple question: How much do you spend annually? If you spend $60,000 per year in retirement, and you have $1.5 million invested in a diversified portfolio, that portfolio can sustain you indefinitely at historical market returns. The logic is clean—but the assumptions embedded in it are where complexity lies.

The 4% rule, a cornerstone of retirement planning, states that you can safely withdraw 4% of your portfolio annually without running out of money over a 30-year retirement. Under this model, a $1.5 million portfolio supports $60,000 annual withdrawals. Working backward, this means: retirement number equals annual expenses divided by 0.04, or equivalently, annual expenses times 25. A worker with $60,000 in annual expenses needs 25 times that amount—$1.5 million—to retire.

But where does the 4% rule come from? Is it actually safe? Are there circumstances where it breaks down? This chapter explores the historical evidence, the Monte Carlo analysis behind it, and the legitimate criticisms raised by researchers and practitioners. You'll learn when the 4% rule is overly conservative and when it's dangerously optimistic.

Variables that reshape your number​

Three core inputs determine your retirement number: annual expenses, investment returns, and life expectancy. Each is more dynamic than it initially appears. Your expenses in retirement may be lower (no commute, no 401(k) contributions, mortgage paid off) or higher (more travel, healthcare, supporting family members). Your expected returns depend on your asset allocation—a bond-heavy portfolio supports a lower number through lower returns, while a stock-heavy portfolio supports a higher number but with greater risk.

Your time horizon matters profoundly. A 40-year-old planning to retire at 45 and live to 100 faces a 55-year retirement—dramatically different from someone retiring at 65 planning to age 85. Healthcare alone becomes a different cost problem at different horizons. This chapter explores each variable, showing you not just how to estimate them, but how to stress-test your assumptions and plan for scenarios where they prove wrong.

Beyond the 4% rule: alternative strategies​

While the 4% rule remains foundational, it's not the only approach. The "guardrails" strategy allows you to adjust spending up or down based on portfolio performance. Dynamic spending strategies link your annual withdrawals to current portfolio values, creating a natural buffer against market swings. Other savers use replacement-rate methods (replacing a percentage of their working income) or segment their portfolios by decade, knowing which portion funds near-term expenses and which funds decades of compounding.

Monte Carlo simulations—probabilistic models that run thousands of retirement scenarios—can give you a percentage probability that your retirement plan succeeds. Are you 90% confident? 99% confident? Different people have different risk tolerances, and understanding the likelihood of your plan is crucial.

Revisiting your number over time​

Your retirement number is not a fixed target calculated once and ignored. As you age, accumulate wealth, and experience life changes, your number will shift. Marriage brings a joint number. Children add expenses, then reduce them. Inheritances may appear. Health crises may demand new spending. Market downturns may force recalibration. This chapter closes by showing you how to revisit and refine your number regularly—annually, or whenever a major life event occurs—ensuring that your target remains realistic and motivating.

Articles in this chapter​