Retirement Calculator

How Does the Retirement Calculator Work?

This retirement calculator projects your financial journey in two distinct phases. During the accumulation phase (your working years), it models your savings growing through contributions and investment returns. During the distribution phase (retirement), it simulates spending down your savings while accounting for inflation-adjusted expenses and Social Security income. The result is a clear picture of whether your money will outlast your retirement.

Understanding Your Retirement Runway

The "Retirement Runway" concept shows what percentage of your retirement is financially covered. A 100% runway means your savings are projected to last through your entire retirement. Less than 100% means savings may deplete before your life expectancy, requiring adjustments to your plan. The animated fuel gauge provides an instant visual indicator of your retirement readiness.

Monte Carlo Simulation Explained

Unlike simple projections that assume a fixed annual return, our Monte Carlo simulation runs 1,000 randomized scenarios using realistic market volatility (12% standard deviation). This accounts for "sequence of returns risk" — the danger that poor market performance in early retirement years can devastate a portfolio even if long-term averages look fine. A success rate above 80% is generally considered a robust plan.

Withdrawal Strategies Compared

• 4% Rule (Fixed): Withdraw 4% of your initial retirement balance in year one, then adjust for inflation each year. Based on the Trinity Study, this historically sustains a 30-year retirement about 95% of the time.
• Dynamic 5% Rule: Withdraw 5% of your current portfolio value each year. Spending automatically adjusts: more in good years, less in bad. This approach can never fully deplete savings but may result in income volatility.
• Your Planned Spending: A fixed spending target (in today's dollars) adjusted for inflation. This matches a specific lifestyle goal but doesn't adapt to market conditions.

Key Assumptions and Limitations

• Returns are nominal: The calculator uses nominal (before-inflation) returns. Real purchasing power is calculated by subtracting the inflation rate.
• Taxes are not included: Withdrawals from traditional retirement accounts are taxed as income. Roth withdrawals are tax-free. Actual spendable income depends on your tax situation.
• Healthcare costs: Medical expenses tend to increase faster than general inflation. Consider budgeting extra for healthcare in later retirement years.
• Social Security adjustments: Benefits receive cost-of-living adjustments (COLAs) annually. This calculator uses a fixed amount for simplicity.

Tips for a Stronger Retirement Plan

• Start early: Compound growth dramatically increases savings over time. Starting 10 years earlier can double your retirement balance.
• Maximize employer match: If your employer matches 401(k) contributions, contribute at least enough to get the full match — it is free money.
• Diversify investments: A mix of stocks, bonds, and other assets can help manage risk while maintaining growth potential.
• Plan for longevity: Many people underestimate life expectancy. Planning to age 90-95 provides a safety margin.
• Consider part-time work: Even modest income in early retirement years can dramatically extend your savings runway.

Frequently Asked Questions