Estimate how long a portfolio can support fixed monthly withdrawals.
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The SWP Duration Calculator helps you Estimate how long a portfolio can support fixed monthly withdrawals. Enter your own values to get an instant result, then use the graph and table to understand how the inputs affect the answer. Calculations run in your browser and are not sent to CalcifyNow.
Enter Starting portfolio, Monthly withdrawal, Expected annual return. The calculator validates the inputs and updates the answer, chart and breakdown without sending your values to the server.
Months supported = −ln(1 − portfolio × monthly rate ÷ withdrawal) ÷ ln(1 + monthly rate). Assumes fixed returns and withdrawals; real market returns vary.
The result is recalculated whenever you change an input. Use consistent units throughout and keep the displayed rounding in mind when comparing with another source.
Use the calculator's pre-filled values as a worked example:
Change one value at a time to see how it affects the result, graph and table.
Read the main result together with the supporting values. The graph shows the relationship visually, while the table makes each step easier to inspect.
Results are estimates and do not include every possible tax, fee, market movement or provider rule unless the calculator specifically lists it. Confirm important financial decisions with current official information.
Estimate how long a portfolio can support fixed monthly withdrawals.
Have these values ready: Starting portfolio, Monthly withdrawal, Expected annual return. Labels beside each field explain the expected unit or format.
It applies the formula shown on this page. Its accuracy depends on the accuracy of your inputs and the assumptions described below the calculator.
Test conservative, expected and optimistic inputs. Compare the payment or outcome as well as the total cost, and remember that rates, fees, taxes and provider rules can change.
Use it as an informed estimate, then confirm important decisions with current official information or a qualified professional.
No. The calculation runs locally in your browser. CalcifyNow does not submit your input values to its database.
Report an issue or suggest another calculator. Your calculation values are never submitted.