Project retirement savings growth with contributions, employer match, inflation adjustment, and Monte Carlo simulation charts.
This calculator projects how a retirement account grows between now and a chosen retirement age. You enter your current balance, monthly contribution, employer match, assumed return, and inflation rate; the tool grows the balance, adds contributions and the match along the way, and reports the result in both nominal dollars and today's purchasing power. It also runs a Monte Carlo simulation, so you get a band of possible outcomes rather than one false-precision number. The figure people most often misread is the inflation-adjusted one: at 3% inflation, a dollar 30 years from now buys only about 41 cents of today's goods.
A concrete input and expected output from the current implementation.
Input
Age 35, retirement at 65. Current balance $50,000. You contribute $500 a month; your employer matches 100% up to $500, so $1,000 goes in monthly. Assumed return 7% per year, inflation 3%.
Expected output
Central projection at 65: about $1.63 million in nominal dollars, and about $670,000 once discounted at 3% inflation into today's purchasing power. The Monte Carlo band spreads around this central path, with edges that shift between runs.
The starting $50,000 compounds monthly at 7% to about $406,000, and $1,000 in monthly contributions grows to about $1.22 million; the two sum to about $1.63 million. Dividing by 1.03^30, roughly 2.43, converts that to about $670,000 in today's purchasing power.
Each month the balance earns interest at the assumed annual return, then your contribution and the matched amount are added, so every dollar, including the match, compounds until retirement. Because the starting balance compounds for the full horizon while later contributions compound for less time, the assumed return dominates the answer: over 30 years, a 1-point change in return moves the result more than a 1-point change in contribution rate.
Instead of one path, the tool runs many simulated return sequences centered on the return you assumed. Each simulation yields an ending balance, and the tool plots them as percentile bands: low percentiles are the bad-luck tail, high percentiles the good-luck tail, and the middle percentile is the typical outcome. The edges shift on every run because the random sequences differ; only the inputs stay fixed.
The 50th percentile is the median: half of the simulated outcomes end above it and half below, so it is the natural central planning case. The 95th percentile assumes you land in the luckiest twentieth of market histories, so treat it as an upside bound, not a budget. Many planners pick a percentile below the median to stay conservative.
Because inflation compounds too. At a steady 3% a year, prices multiply by 1.03 to the 30th power, about 2.43 times, over three decades, so the nominal balance is divided by that factor and buys roughly 41% of what the same dollars buy today. The inflation-adjusted figure is the honest one to compare against today's expenses; the nominal figure is what the statement will literally say.
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