The projection runs your plan a thousand times over different market sequences. Here is what each number it reports back is actually claiming.
Success %
The share of runs that funded every obligation all the way to your end age: spending, one-time expenses, income tax, and insurance premiums alike. A single unfunded dollar in a single year fails that whole run.
So it is a pass/fail tally, not a margin of safety. It says nothing about how the failures failed. That is why the next number exists.
Failure depth
When runs do fail, the app also reports the typical depletion age and the total shortfall, measured across the failing runs only. Two plans can both succeed 85% of the time and be nothing alike: one runs a little short at 93, the other is empty at 78. Read the pair together, never the success rate alone.
The median and the bands
The median is the middle outcome. Half the runs did better, half worse. It is not a forecast, and no single year of it is a promise.
Turn on the probability fan and you see the spread around it:
- The 25–75 band is the everyday range: half of all runs landed inside it.
- The 10–90 band is the stretch: falling outside it is about a 1-in-10 result, in either direction.
The 90% downside readout states that lower edge as one number: the 10th-percentile ending value, or, once more than 10% of runs fail, the age by which that run is out of money.
Per-age numbers are medians too
Every column of the year-by-year table is the median for that age, taken across all runs. Neighboring rows can come from different runs, so they do not add up the way one household's actual years would.
To follow a single coherent path instead, zero the volatility inputs. The Trace: zero volatility button does it in one click, and the medians collapse onto that one path exactly. See why re-running gives the same answer.
When the three models disagree, the disagreement is the finding: it tells you the answer depends on which market history you believe, which is worth more than any single success rate.