Monte Carlo Simulator

Explore the range of outcomes a portfolio might have produced, rather than a single projection. This runs 1,000 simulations, each drawing a different sequence of real historical market years, and shows where those paths ended up. You can set a starting balance, a monthly amount to add or withdraw, and a time horizon. The spread reflects how much the order of returns matters — not a forecast.

Years
5 10 15 20 25 30
Advanced options
Historical pattern
Short Typical Long cycles
Preserves typical multi-year market cycles. Typical is the default.
＋ Add one-time cash event (bonus, inheritance, large withdrawal…)
How this works

Each of the 1,000 scenarios is built by drawing real multi-year stretches of S&P 500 history at random and stringing them together — not by assuming a bell curve or a fixed average return. Returns come from the Shiller dataset, covering more than 150 years.

Historical pattern

Real markets don't reset each year. A downturn tends to last two to three years; an expansion can run much longer. This setting controls how much of that continuity each scenario keeps.

  • Short — each year is drawn independently, with no memory of the year before. Produces the narrowest range, and understates how long a good or bad stretch can persist.
  • Typical — draws three years at a time, so a scenario that picks up 2008 also picks up the 2009 recovery. Preserves ordinary recession-and-recovery cycles.
  • Long cycles — draws five years at a time, which can pull in a full expansion and contraction such as 1999–2003. Produces the widest range.

Reading the result

The shaded band spans the 10th to 90th percentile of outcomes: eight scenarios in ten finished inside it. The line through the middle is the median. A wide band means the outcome depends heavily on which years you happen to get.

Withdrawals are taken monthly. If a scenario's balance reaches zero it is recorded as depleted, and the depletion rate is reported alongside the percentiles.