How to use the savings runway calculator
This tool is for exploring a household cash-flow scenario using numbers you choose. Begin with money that is actually available for this purpose. Enter monthly living costs and other monthly income in the same currency. Other income can represent a pension, earnings or another regular source, but the calculator does not decide whether you qualify for any payment.
The chart above the inputs updates as you type or move a slider. Open the additional settings to change return, inflation or the time span. Hover, touch or use the arrow keys on the chart to inspect a month. These values use the same monthly model as the calculated summary. Select Calculate to confirm the summary and enable Copy result. Editing any input clears that confirmation while updating the live chart. Use example restores the illustrated scenario; Clear restores the entry examples while preserving the currency.
What the result means
If a planned withdrawal uses the remaining savings, the result identifies that month and stops the schedule there. Month 1 starts now. Fully covered months counts months in which savings plus income meet all living costs. When the last withdrawal is larger than the balance, the unfunded cost shows the gap; the calculator does not borrow money to cover it.
An ending balance above zero means the savings lasted through the selected period under these assumptions. It does not establish an unlimited lifetime. Today's money divides the nominal ending balance by the cumulative inflation factor, making purchasing power easier to compare with the starting balance. The chart and expandable monthly table use the same calculation. Copy result captures the summary and assumptions.
Monthly calculation and timing
The monthly return is (1 + annual return / 100)^(1/12) − 1. The monthly price factor is (1 + annual inflation / 100)^(1/12). This treats each annual percentage as an effective annual rate rather than dividing it by twelve. Monthly costs begin at the amount you entered and change by the price factor for each later month.
At the beginning of each month, costs minus fixed income are withdrawn. If income is larger, the surplus is deposited. The remaining balance then receives one month of return. Inflation-adjusted balances use the price level at that month's end. No intermediate amount is rounded to cents; display rounding is applied only when showing or copying results.
Two examples you can check
With 12,000 in savings, monthly costs of 1,000, no income, zero return and zero inflation, twelve withdrawals are fully covered. Savings reach zero at the start of month 12, with no unfunded cost in that month. With 500 in savings and the same costs, month 1 has an unfunded cost of 500.
With no starting savings, costs of 100 and fixed monthly income of 200, zero return and zero inflation, the monthly surplus adds 100. After one year, the nominal balance is 1,200. This illustrates why an initial zero balance does not automatically mean expenses cannot be met.
Limits and useful comparisons
Compare one changed assumption at a time, such as a smaller monthly cost or lower return. The model uses a constant return; it does not reproduce volatile markets or the order of investment gains and losses. Income never rises automatically. Taxes, fees, irregular expenses and changing benefit rules are outside the model.
Amounts are limited to one billion, the horizon to 100 whole years, return to −99% through 100%, and inflation to −50% through 100%. Scenarios exceeding one quadrillion in a calculated amount are rejected. Use a dot or comma for decimals and omit thousands separators. The currency setting changes formatting only.
Frequently asked questions
Is this a safe withdrawal recommendation?
No. It is a mathematical scenario using your inputs and provides no investment or payment guarantee.
Why does a zero balance sometimes cover the final month?
An exact withdrawal can pay that month's costs completely. The result distinguishes this from a withdrawal with an unfunded remainder.
Does inflation also increase my income?
No. Income is fixed in nominal terms. Only living costs follow the inflation assumption.
Are my amounts saved?
No financial inputs or results are saved by this tool. Refreshing the page starts a new scenario.
Can I change the withdrawal date?
This version always applies cash flow at the start of the month. A different timing convention can produce a different answer.
Calculation background: Investor.gov: Compound Interest Calculator