How Retirement Planning Works
Retirement planning answers a deceptively simple question: will your savings last? The challenge is that the answer depends on variables that span decades — how much you save, how markets perform, how inflation erodes purchasing power, and how long you live. Small changes in any of these assumptions compound dramatically over a 20-40 year retirement.
This calculator models the accumulation phase (your working years, when you are saving and investing) and the drawdown phase (retirement, when you are spending from your portfolio). It tracks your portfolio balance year by year, accounting for contributions, investment returns, inflation, and withdrawals, to project whether your money outlasts your retirement.
The Safe Withdrawal Rate
The safe withdrawal rate (SWR) is the percentage of your portfolio you can spend each year in retirement without running out of money. The most well-known guideline is the “4% rule,” originating from William Bengen's 1994 research, which found that a 4% initial withdrawal rate (adjusted annually for inflation) survived every 30-year period in U.S. market history from 1926 onward.
The 4% rule is a useful starting point, but not a universal law. Your safe withdrawal rate depends on your asset allocation, time horizon, flexibility to reduce spending in downturns, and whether you have other income sources like Social Security or pensions. A longer retirement (40+ years for early retirees) may require a lower rate of 3-3.5%, while a shorter retirement or flexible spending plan may support 4.5-5%.
Why Inflation Matters
Inflation is the silent risk in retirement planning. At 3% annual inflation, the purchasing power of $1 is cut in half in about 24 years. This means that $60,000 of annual spending today requires roughly $120,000 in 24 years to maintain the same lifestyle.
This calculator adjusts your retirement spending for inflation each year, using the rate you specify (the default is the Federal Reserve's 2% long-run target). If you want to see a more conservative scenario, try 3% — the historical average over the past century is closer to 3% including periods of high inflation in the 1970s and 1980s.
Sequence of Returns Risk
The order in which investment returns occur matters enormously during retirement. Two portfolios can have the same average return over 30 years but produce wildly different outcomes depending on whether bad years come early or late. A market crash in the first few years of retirement — when your portfolio is at its largest and you are withdrawing from it — can permanently impair your financial plan.
This is called sequence-of-returns risk, and it is the primary reason why average return assumptions can be misleading. This calculator uses a constant return model for simplicity, but be aware that real-world volatility adds risk beyond what a flat projection shows. Building a buffer (saving more than the minimum) is the best defense against bad early returns.
How to Use This Calculator
Enter your current age, retirement age, current savings, and monthly contribution. Set your expected annual spending in retirement and your planning end age (how long you want your money to last). The calculator projects your portfolio balance each year and tells you whether your savings survive to the end.
Experiment with different assumptions: try increasing your monthly contribution by $200, or see how retiring two years later changes the outcome. The portfolio trajectory chart makes it easy to visualize when your money peaks and when it depletes. All inputs are saved in the URL for easy comparison.
FAQ
- How much do I need to retire?
- A common guideline is 25 times your annual spending (the inverse of the 4% rule). If you spend $60,000 per year, that means a target of $1.5 million. But this is a rough estimate — the right number depends on your age, health, income sources, risk tolerance, and whether you plan to leave an inheritance. Use this calculator to model your specific situation.
- What investment return should I assume?
- A balanced portfolio of stocks and bonds has historically returned 6-8% per year before inflation (4-6% after inflation). For conservative planning, use 5-6% nominal. For aggressive planning with an all-stock portfolio, 8-10% is historically reasonable but comes with more volatility. The calculator defaults to a moderate estimate.
- Does this calculator include Social Security?
- This calculator models your personal savings and investments. It does not automatically include Social Security, pension income, or other fixed income sources. To account for these, you can reduce your annual spending by the expected benefit amount — for example, if you expect $20,000/year from Social Security, enter your total spending minus $20,000.
- What if I want to retire early?
- Early retirement (before age 59.5) means a longer drawdown period and potentially no access to tax-advantaged accounts without penalties. The 4% rule was designed for 30-year retirements. For a 40-50 year retirement, consider a withdrawal rate of 3-3.5%. This calculator lets you set any retirement age and planning horizon to see if the math works.
- How does inflation affect my retirement plan?
- Inflation erodes purchasing power over time. At 3% inflation, you need roughly double the income in 24 years to maintain the same lifestyle. This calculator increases your annual spending by the inflation rate each year to show the real cost of retirement, not just the nominal cost in today's dollars.
- What is the biggest risk to my retirement plan?
- Sequence-of-returns risk — experiencing poor investment returns in the first few years of retirement — is the most dangerous factor. A market crash early in retirement can deplete your portfolio faster than average returns suggest. Other major risks include inflation running higher than expected, healthcare costs, and living longer than planned.