Open Vanguard’s retirement calculator. Type in your age, your savings, your monthly contribution. Hit “calculate.” You’ll get a single line: a smooth, confident curve from now until age 95.
That line is the median outcome of an implicit simulation. It’s what the model thinks is most likely to happen. But “most likely” is doing a lot of work in that sentence. The model considers thousands of possible futures, and the line is the one in the middle.
Half of you are above. Half are below.
Half of the simulated futures end with you holding more money than the line. Half end with you holding less. The 5th-percentile path, the bad-but-not-disastrous case, can be drastically below the line. The 95th-percentile path can be drastically above.
The picture above is one plan. A 35-year-old, €50k saved, contributing €500/month, retiring at 67 with a €1,200/month pension. A “single line” calculator would show only the median, the accent line through the middle. RetireSafe shows the same plan as a fan: the outer band is where the 5th and 95th percentile of simulated futures land.
A calculator that hides that range hides the actual decision you’re making. “Will I have €450k at age 85?” is the wrong question. The right question is: “What’s the range of plausible outcomes, and which end of the range am I willing to plan around?”
What we do instead
RetireSafe runs 10,000 simulated futures every time you click Run. We show you the median and the P5/P25/P75/P95 percentile bands. You see the fan, not a line. The honest answer is in the shape of the fan, not its centre.
That’s the whole pitch. Every other feature is downstream of this single design decision: the ranking of what threatens your plan, the what-if scenarios, the breakdown of why the failing futures failed. Show the uncertainty instead of hiding it.