Planning Studio
Monte Carlo Explorer
Investment Growth shows one possible path under one fixed assumed return. This tool instead runs many randomized paths and shows the full range of plausible outcomes — including what happens if you start withdrawing money and a bad year lands early.
Your assumptions
The amount you're starting with today.
Added once per year, during the accumulation phase (before any withdrawal phase begins).
The average of the simulated distribution of annual returns. Illustrative, not a forecast.
How much annual returns swing around the mean. Set to 0% to remove randomness entirely.
Turns this on to see sequence-of-returns risk: a bad early withdrawal year compounds differently than a bad late one, even with the same average return.
Note this number down to reproduce this exact run later. The same seed with the same other inputs always produces the identical result.
Simulated results
Running the first simulation…
Outcome range over time
Waiting on the first simulation to finish…
How sequence-of-returns risk works
Every simulated trial draws a random return for year 1, then year 2, then year 3, and so on, strictly in that order — never shuffled or averaged in advance. During any withdrawal phase, that year’s withdrawal is subtracted after that year’s return has already changed the balance.
Worked example: say a $100,000 balance experiences a −20% return in year 1 and then withdraws $8,000. The balance falls to $80,000 from the return, then to $72,000 after the withdrawal — that $72,000 is now the base every later year’s growth compounds from. If that same −20% year had instead landed in year 20, after two decades of growth had already built a much larger balance, the SAME $8,000 withdrawal and the SAME −20% return would barely dent the larger balance by comparison. The average return across the whole horizon can be identical in both cases — the order the returns arrive in, relative to the withdrawals, is what changes the outcome. This is why two trials with the same average simulated return can end at very different balances once withdrawals start, and why the percentile band above is a more honest picture than any single average-return number.
Illustrative only — not a guarantee
This tool produces an illustrative, hypothetical projection based entirely on the numbers you enter. It is not a guarantee or prediction of future results, and it is not personalized investment, tax, or legal advice. Every assumption shown here (contribution amount, assumed rate of return, inflation, fees, and time horizon) is fully editable and has not been validated against your actual financial circumstances, goals, or risk tolerance.
Dollar figures are nominal (not adjusted for inflation) unless a figure is explicitly labeled real / inflation-adjusted. Actual investment results will vary and may be significantly lower or higher than any figure shown here.
Results from this tool may vary with each use and over time: changing any input, or running this same tool again later as your numbers or the markets change, can produce a different outcome than the one shown here.
A hypothetical modeled range, not a forecast or guarantee
The percentile band and every number on this page come from a randomized simulation of 1,000 hypothetical paths, built entirely from the mean return, standard deviation, and other assumptions you entered above. It is not a forecast, prediction, or guarantee of what will actually happen to any real investment — it is a way to see a RANGE of plausible outcomes under one set of assumptions, instead of a single misleadingly precise number. Changing the mean return, standard deviation, or random seed will change every figure shown here.