Calculator
How long will my money last?
See how many years a portfolio lasts if withdrawals rise with inflation and the return stays constant, plus the withdrawal that would hold purchasing power.
The monthly step
The withdrawal starts at one-twelfth of the annual spending you type. Each month the model takes the withdrawal from the balance, then grows the remainder at the monthly version of your nominal return. The withdrawal itself steps up with monthly inflation. The horizon stops at 60 years. A portfolio still positive then is reported as lasting through the horizon, which is not the same phrase as lasting forever, even though a constant surplus return would.
Pair this with the 4% rule page before you treat a long bar as permission to retire.
Read what the 4% rule actually tested
Questions
Why can the same 4% last forever here and still be risky?
This page uses one return every year. If that return is comfortably above inflation, a 4% withdrawal never loses purchasing power in the model, so the balance never hits zero. Historical 4% research was about surviving the worst actual sequences, including years when markets fell while you were selling. A flat return cannot show that. If the result says the money lasts, read it as 'under this constant rate,' not as safety.
What is the perpetual withdrawal?
It is the real return on the balance, paid out over the year. Spend only that, and the model keeps the purchasing power of the principal. Spend more, and you are spending principal. At a 7% nominal return and 3% inflation the real return is about 3.9%, so the perpetual annual amount is about 3.9% of the balance, not 7%.