What Is a Retirement Savings Longevity Calculator?
A retirement savings longevity calculator answers one of the most important questions in financial planning: how long will my money last? By combining your current savings balance, planned monthly withdrawals, expected investment returns, and the rate of inflation, the calculator projects the number of months and years your nest egg can sustain your lifestyle.
Unlike simple division (savings divided by monthly spending), this tool accounts for the fact that your remaining balance continues to earn returns while you draw it down. It also factors in inflation, which gradually reduces the real value of every dollar. The result is conditional on those inputs; adding a return assumption does not establish forecast accuracy.
How to Use This Calculator
- 1
Enter Your Savings
Type the total amount you have saved for retirement. Include 401(k), IRA, brokerage, and any other investment accounts you plan to draw from.
- 2
Set Monthly Withdrawal
Enter the amount you plan to withdraw each month. If you receive Social Security or a pension, subtract that income first and enter only the gap your savings must cover.
- 3
Specify Annual Rate of Return
Enter the annual return you expect from your portfolio. The 6% default is a hypothetical effective annual rate, not a promised or recommended return. Use a net-of-fees assumption if fees will reduce the balance.
- 4
Add Inflation Rate
Enter the expected annual inflation rate. The 3% default is an example, not a forecast. Higher inflation means your savings lose purchasing power faster.
- 5
Click Calculate
Press the Calculate button to see how many months and years your savings will last, plus the total amount withdrawn over that period.
Understanding the 4% Rule and Withdrawal Rates
William Bengen's 1994 historical research examined initial withdrawals followed by inflation adjustments across historical U.S. stock-and-bond periods. A commonly cited starting withdrawal is 4% of the initial portfolio; this is a historical scenario result, not a success probability produced by this calculator. For a $500,000 portfolio, that works out to $20,000 per year or about $1,667 per month.
While the 4% rule is a useful starting point, it was based on historical U.S. market data and assumes a specific asset allocation. Your personal withdrawal rate should depend on your age at retirement, life expectancy, risk tolerance, other income sources, and current market valuations. See Bengen's original withdrawal research. A constant return suppresses sequence risk: early losses during withdrawals can have different consequences from later losses even when average returns match.
Why Use Our Retirement Savings Longevity Calculator?
Inflation-Adjusted Projections
Uses the Fisher equation to compute real returns so your projection uses today's purchasing-power units under the entered assumptions.
Instant Scenario Testing
Adjust any input and recalculate immediately to compare different withdrawal rates, return assumptions, or inflation scenarios.
Clear Timeline
See modeled depletion months, full scheduled withdrawals, any partial final payment, and total real withdrawals within the 100-year horizon.
Local Calculation
The calculation has no API request or saved-input feature. Site analytics and other request handling are described in the privacy policy.
Tips for Making Your Retirement Savings Last Longer
Compare lower and higher spending assumptions, rather than treating a single date as a retirement plan. Fixed returns do not model market downturns, spending shocks, taxes, required distributions, or changes in benefits. A flexible withdrawal plan requires additional rules that this tool does not simulate.
For eligible U.S. workers, SSA explains delayed retirement credits after full retirement age until 70. Claiming later also leaves a period without those benefits; this calculator does not compare lifetime benefit strategies or household eligibility.
Formula and a zero-return check
With annual return R and inflation I expressed as decimals, monthly real growth is g = [(1 + R) / (1 + I)]^(1/12). Each month grows the balance by g and then withdraws the smaller of the requested amount or available balance. Both the withdrawal and displayed balance use today's dollars.
With $10,000, $3,000 monthly withdrawals, zero return, and zero inflation, three full withdrawals use $9,000 and a fourth partial withdrawal uses $1,000. The tool reports depletion in month four, not four fully funded months. With equal annual return and inflation, real growth is zero, giving the same result.