Monte CarloInvestment simulator.
A single growth rate hides the truth: markets are noisy, and the same plan can land almost anywhere. This runs thousands of possible futures to show the realistic range — from a bad run of luck to a great one.
Investing $10,000 today plus $500 a month for 25 years — paying in $160,000 across 1,000 simulated futures.
Range of outcomes over time
Shaded bands show where the middle 80% (light) and middle 50% (dark) of simulated paths land each year. The violet line is the median; the dashed line is the cash you paid in.
Distribution of outcomes at year 25
Returns compound, so outcomes are skewed: most paths cluster lower with a long tail of high results — which is why the best case sits much further from the median than the worst case does.
How this works. Each path models monthly returns as Geometric Brownian Motion — lognormal steps with the drift and volatility you set above. It assumes constant parameters and normally distributed log-returns, and ignores fees, tax, and inflation. It’s an illustration of uncertainty, not a forecast or financial advice.