You have a pot and you spend from it. This runs that through every start year in the historical record and reports how often it reached 100 — and, when it didn't, at what age it ran out.
The answer
age 81
35 of 58 historical start years ran out before age 100 — 39.7% did not. The median failure lands at age 81, and a plan that runs dry at 94 is a very different plan from one that runs dry at 68.
In 39.7% of 58 sampled sequences, under this model and these assumptions, the plan funded its floor spending every year for 40 years. ±6.4 points is sampling error alone.
What the money does
What this calculator assumed, because you weren't asked
United States, 1928–2024 (97 years) · Damodaran (NYU Stern), Annual Returns on Stock, T.Bonds and T.Bills: 1928–current · retrieved 2026-08-08
This is one country's record, and it belongs to the most successful equity market of the twentieth century. Anyone whose future resembles it will be fine; that is not the same as a promise.
This is a modelling tool, not financial advice. It never names an investment and takes no money from anyone who sells one.
A pension that starts at 67, a mortgage that ends in 2034, a partner who stops working two years after you, a year of university fees, tax. The full app takes all of it, keeps every figure on your own device, and tells you which change moves the answer most.