How long will my retirement savings last?
The estimate depends on your starting balance, monthly withdrawal, return, inflation and payment timing. End-of-month withdrawals apply the return before the payment; beginning-of-month withdrawals take the payment first.
Payment periods n = −ln(1 − r × balance / withdrawal) / ln(1 + r)
Rates in the formula are decimals. At zero return, n is simply balance ÷ withdrawal. Beginning-of-month payments use withdrawal × (1 + r) in the denominator of the fraction inside the logarithm. The result reports the actual scheduled month of the last withdrawal; a partial last payment is counted separately.
Worked example: a straightforward baseline
With $120,000, a $1,000 monthly withdrawal, no return, and no inflation adjustment, the balance supports 120 payments. With end-of-month payments, the last payment is at month 120: 10 years after the start. With beginning-of-month payments, the last payment is at month 119.
Use more than one scenario
Try a smaller withdrawal to see what flexibility changes. Then reduce the return and increase inflation. This tool applies the same rate every month, so it does not measure the effects of a market decline early in retirement, variable expenses, taxes, or investment fees beyond those already reflected in your return input.
To solve for a monthly amount over a chosen number of years, use the retirement withdrawal calculator. For a simple starting-rate illustration, read the 4% rule guide.
Questions about this calculation
How long will my savings last in retirement?
Enter your balance, monthly withdrawal, return and inflation assumptions to estimate the timeline. With no return and no inflation adjustment, $120,000 divided by a $1,000 withdrawal supports 120 full monthly payments. Payment timing determines the date of the last withdrawal; changing the assumptions changes the result.
What does “does not run out” mean?
It means the assumed constant return covers every modeled withdrawal. Real investment returns change, so this is a mathematical condition, not a guarantee that a portfolio will last forever.
Should I subtract Social Security or other income?
Enter the amount that must come out of the portfolio. If your planned spending is $4,000 a month and you choose to assume $1,500 of other spendable income, enter a $2,500 withdrawal. This calculator does not estimate those benefits or their taxes.
Does the chart include inflation?
When inflation adjustment is enabled, the calculator uses an exact real return and shows balances in today’s purchasing power. This models withdrawals that grow monthly with inflation. When it is disabled, withdrawals stay fixed and balances are nominal dollars.
Methodology and sources
Model reviewed October 25, 2026. Formulas and the worked example are derived from the monthly cash-flow equation; see the complete calculation methodology. No market forecast or historical success rate is assumed.
For general retirement-withdrawal context: Fidelity, “How can I make my savings last?”, article dated May 26, 2026; reviewed October 25, 2026. Our model is an educational illustration and is not affiliated with Fidelity.