The most persuasive part of a calculator is often its most fragile: a precise answer. “Twenty-one years” feels more knowable than “it depends.” Yet the precision comes from the arithmetic, not from certainty about the future.
Name the problem you are trying to avoid
Howard Marks’s Risk Revisited Again distinguishes volatility from the possibility of permanent loss. We would extend that question to a household goal: what outcome are you trying to avoid? The answer might be selling at an inconvenient time, returning to unwanted work, or finding that essential spending costs more than expected.
Those outcomes are not interchangeable. Someone who can reduce discretionary travel has different flexibility from someone whose spending is mostly housing and care. Two people can enter the same annual spending in a calculator and still have very different exposure to disappointment. The number needs a short explanation of what it includes.
Separate the target from its reliability
In this planner, $40,000 of annual spending divided by a 4% withdrawal assumption produces a $1,000,000 target. At 3.5%, the same division produces about $1,142,857. That is arithmetic. Neither result establishes that a portfolio will support every possible retirement.
The model estimates an accumulation path using a constant real return and contributions at the end of each month. It does not run a retirement withdrawal simulation. In particular, it cannot tell you how a bad sequence of returns after leaving work would affect a spending plan. Reaching the line and sustaining withdrawals are separate questions.
Leave a decision trail
Try the two withdrawal assumptions and record the difference in target and timeline. Add a note outside the calculator about why you chose the spending figure and which expenses might change. You now have something to revisit when your circumstances shift, rather than an unexplained number to defend.
Before treating a result as a decision to stop working, identify the questions this tool cannot answer: taxes, healthcare, the length of retirement, irregular expenses, and the actual investment and withdrawal approach. A useful next conversation is one that starts with those gaps. The purpose of the chart is to make your questions better, not to end them.
Read the original.
- Oaktree · Risk Revisited Again ↗ (opens in a new tab)
Howard Marks, June 8, 2015. Start with “What Risk Really Means.”
The FIRE application and exercises are FireFolio’s original interpretation. No affiliation or endorsement is implied. Sources checked September 20, 2026. Educational material, not individualized investment advice.