Monte Carlo Retirement Simulation

Run 1,000 simulated versions of retirement, each with a randomly varying annual return, to see what share of them didn't run out of money.

Simulation results depend heavily on the assumptions entered (expected return, volatility, and the assumption that returns are normally distributed and independent each year) and are not predictions of actual investment performance. This is a deterministic illustration (a fixed random seed), not a live re-randomized forecast.

Starting portfolio value

Initial withdrawal rate

Inflation (withdrawal increases)

Expected annual return

Return volatility (std. dev.)

Retirement duration, years

Number of simulations

Success rate (didn't run out of money)

64%

10th percentile ending balance

Median ending balance

$395,196

90th percentile ending balance

$4,001,653

Based on 1,000 simulated trials, each drawing a random annual return from a normal distribution around your expected return and volatility. The shaded band shows where 80% of simulated outcomes fell each year.

How it works: instead of assuming the same return every year (like the Retirement Income calculator), each simulated trial draws a different random return each year from a normal distribution around your expected return and volatility, then applies the same withdrawal mechanics. The success rate is the share of trials where the portfolio lasted the full duration.

Limitations: real market returns aren't independently drawn from a normal distribution every year (they cluster and have “fatter tails” than a normal curve predicts), and this doesn't model taxes, fees, or changing spending needs. Success rate is rounded to a whole percent deliberately — treat it as a rough illustration, not a precise probability.

Sources & further reading

Center for Retirement Research at Boston College: How Long Will Retirement Savings Last?