What the question involves
A sustainable spending level is the most you could spend each year, rising with inflation, and still have the money last in most futures. “Most” is your choice: aiming for the money to last in nine futures out of ten supports less spending than aiming for three out of four, and usually leaves more unspent.
What this tool computes
The same search the Strategy Lab uses: it tries spending levels, halving the gap each time, until it finds the highest one (to the nearest thousand dollars) whose success rate meets your target. Each level is tested on 400 simulated market paths, all the same markets, with taxes, required withdrawals and health costs in every run.
What it leaves out
Spending here never adapts to markets. Real retirees cut back after bad years, which supports a higher starting amount; the Strategy Lab can solve for that with guardrails spending. Pensions, state income tax and one-off costs are left out of this quick version.
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This page explains how the rules work. It is not financial, tax or investment advice. Disclaimer