How to Calculate the Lifespan of Your Retirement Savings [2026]

Safety Note: Financial planning involves market risk and personal variables. This guide is for educational purposes and does not replace professional financial advice.

Quick takeaway: Your money's lifespan depends on a balancing act between your starting balance, annual withdrawals, investment returns, and inflation. If you start with $500,000, withdraw $25,000 yearly, earn a 5 percent return, and face 3 percent inflation, your funds will last roughly 25 years. Use Babbage Calculator's Time Value Of Money Tvm Calculator to run your exact numbers and build a secure financial plan.

Figuring out how long your savings will last is the most important question in retirement planning. You need a clear mathematical framework to ensure you do not outlive your assets.

The Core Formula and Worked Example

The basic math relies on the Time Value of Money. The core variables are Present Value (your starting savings), Payment (your annual withdrawal), Rate (your investment return minus inflation), and Number of Periods (years).

Let us look at a real worked example to see how these variables interact.

Starting savings: $1,000,000 Annual withdrawal: $40,000 Expected annual return: 6 percent Expected annual inflation: 2.5 percent Real return rate: 6.0 - 2.5 = 3.5 percent

If you withdraw $40,000 at the start of each year and the remaining balance grows at a real rate of 3.5 percent, the money will last approximately 41 years.

However, if inflation spikes to 4 percent, your real return drops to 2 percent. Under those new conditions, the exact same $1,000,000 portfolio runs out in about 34 years. This demonstrates why adjusting for both growth and inflation is necessary before making long-term commitments.

Understanding the Time Value of Money

The Time Value of Money is a fundamental principle in finance. It states that a dollar today is worth more than a dollar in the future because of its earning potential. When you leave money invested, it generates returns. Those returns then generate their own returns, creating compound growth.

As explained in 4 Steps to Consider the Time Value of Money in Retirement Planning, this compounding effect is the engine that keeps your portfolio alive while you take regular distributions.

At the same time, inflation works against you. The article The Time Value of Money: How It Affects Your Retirement Savings highlights that while interest and investment returns grow your nominal balance, inflation steadily erodes the actual purchasing power of those dollars. You must account for both forces to get an accurate picture of your financial longevity.

How Inflation Eats Your Savings

Inflation is the silent drain on retirement accounts. If your living expenses are $50,000 today, a 3 percent annual inflation rate means you will need nearly $67,000 to buy the exact same goods and services in ten years.

The Report to Congress The Impact of Inflation on Retirement Savings December 2024 - U.S. Department of Labor details how high inflation periods can severely reduce the lifespan of savings and investments by forcing retirees to withdraw larger amounts just to maintain their standard of living.

When calculating your money's lifespan, never use a zero percent inflation rate. Always subtract a realistic inflation estimate from your expected investment return to find your "real" rate of return.

Finding Your Safe Withdrawal Rate

For decades, financial planners relied on the "4 percent rule." This guideline suggested that if you withdrew 4 percent of your initial portfolio value in the first year of retirement and adjusted that dollar amount for inflation every subsequent year, your money would likely last 30 years.

Recent market conditions have prompted researchers to adjust this figure. According to Safe Withdrawal Rate 2026: New Research Says 3.7%, Not 4% - SafeMoney.com, a slightly more conservative rate of 3.7 percent is now recommended for a standard balanced portfolio over a 30-year horizon.

Similarly, What's a Safe Retirement Withdrawal Rate for 2026? - Morningstar suggests a 3.9 percent starting withdrawal rate for new retirees seeking consistent, inflation-adjusted spending with a high probability of success.

If you have $800,000 saved, you can use Babbage Calculator's Percentage Calculator to find that a 3.9 percent initial withdrawal equals $31,200 for your first year.

Market Performance and Sequence of Returns

Average returns do not tell the whole story. The order in which you experience investment returns matters immensely. This concept is known as sequence of returns risk.

As detailed in Sustainable withdrawal rates in retirement - RBC Wealth Management, your asset allocation and the specific market conditions during the early years of your retirement heavily influence portfolio sustainability.

Expert Insight: Sequence of returns risk can derail even the best retirement plans. If the stock market drops significantly during your first few years of retirement, withdrawing fixed amounts forces you to sell more shares at low prices. This permanently shrinks your portfolio's earning power, making it much harder to recover when the market eventually rebounds.

To mitigate this risk, many retirees keep one to two years of living expenses in cash or short-term bonds. This prevents them from selling stocks at a steep loss during a market downturn.

Choosing a Withdrawal Strategy

Your withdrawal strategy dictates how you pull money from your accounts year after year. The guide on Retirement withdrawal rules and strategies - BlackRock outlines several distinct approaches.

Fixed-dollar strategy: You withdraw a specific dollar amount every year, adjusting only for inflation. This provides predictable income but ignores market performance.

Fixed-percentage strategy: You withdraw a set percentage of your portfolio's current value each year. If the market drops, your income drops. If the market rises, your income rises. This ensures you never entirely run out of money, but your standard of living will fluctuate wildly.

Bucket strategy: You divide your money into different "buckets" based on when you need it. Short-term needs sit in cash, medium-term needs in bonds, and long-term needs in stocks. This helps manage sequence of returns risk while still capturing growth.

Factoring in Other Income and Costs

Your investment portfolio is rarely your only source of funding. To accurately calculate how long your money will last, you must factor in outside income streams and specific liabilities.

The guide Preparing for Retirement | U.S. Department of Labor emphasizes the need to understand employer retirement plans, Social Security benefits, and pensions.

If your total annual expenses are $60,000, but you receive $25,000 from Social Security and a $10,000 pension, your portfolio only needs to cover the remaining $25,000 gap. This drastically extends the lifespan of your savings.

You must also account for taxes. Traditional IRA and 401(k) withdrawals are taxed as ordinary income. If you need $25,000 in spending money, you might need to withdraw $30,000 to cover the tax bill. Healthcare costs, including Medicare premiums and out-of-pocket expenses, also tend to rise faster than general inflation and must be modeled into your long-term plan.

Common Mistakes

The most frequent error is assuming a static, high rate of return. Markets are volatile. Assuming a constant 8 percent return every year will give you a false sense of security.

Another mistake is forgetting to adjust for inflation. A $50,000 withdrawal might feel comfortable today, but it will not cover your basic needs in twenty years.

Retirees also frequently underestimate their lifespan. Planning for your money to last until age 85 is risky if family history and health indicators suggest you could easily live to 95. It is always safer to plan for a longer time horizon.

Finally, rigid thinking causes problems. Refusing to lower your withdrawal rate during a severe market recession can permanently damage your portfolio's ability to generate income.

Regular Review and Adjustments

A retirement plan is not a document you create once and forget. It requires ongoing maintenance. The U.S. Department of Labor's Preparing for Retirement resource stresses the importance of reviewing your financial plans annually.

Economic conditions change. Inflation rates fluctuate. Tax laws are updated. Your personal health and spending desires will evolve. By reviewing your portfolio balance, recalculating your safe withdrawal rate, and adjusting your spending habits each year, you can keep your financial plan on track.

Use Babbage Calculator's Time Value Of Money Tvm Calculator annually to run fresh scenarios based on your current balance. Staying adaptable is the best way to ensure your money lasts as long as you do.