Free Online Monte Carlo Simulation Tool — Retirement & Investment Calculator
QuantCalc is a free online Monte Carlo simulation tool for retirement and investment planning. Each run replays your plan across 10,000 correlated market simulations — different sequences of good and bad years drawn from the expected return, volatility, and correlation of your asset classes — and reports the probability your money lasts, plus the full range of ending balances. It runs in your browser with no signup, no download, and no account.
Enter your age, savings, contributions, and retirement spending. Pick an allocation and a published forecast. Get your plan's success rate in seconds.
Run a Free Monte Carlo Simulation →No signup. No download. Free to run.
What this Monte Carlo simulation tool does
10,000 trials per run
Every simulation computes 10,000 market paths with correlated asset-class returns, so one lucky (or unlucky) sequence never decides your answer.
Sobol quasi-Monte Carlo
Sampling uses Sobol low-discrepancy sequences, which fill the outcome space more uniformly than plain pseudo-random draws — tighter estimates from the same number of trials.
Forward-looking forecasts
Return assumptions come from capital market expectations derived from research published by J.P. Morgan, BlackRock, Vanguard, GMO, Schwab, and Invesco — not just a historical average.
Tax-aware, free
Federal taxes, RMDs, IRMAA surcharges, and ACA subsidy effects are modeled in the free tier — the tax engine is not paywalled.
A Monte Carlo investment calculator, not a flat-return projection
A fixed-return calculator assumes the market delivers its average every single year. Real markets do not: the same average return with a crash in year one produces a very different retirement than the same crash in year twenty. A Monte Carlo investment calculator captures that sequence-of-returns risk by simulating thousands of alternative market histories and counting how many your plan survives.
The output is a success rate — the share of simulated paths where your portfolio funds your full plan — alongside percentile bands for the ending balance, so you can see the plausible best, middle, and worst cases rather than a single number.
Run a Monte Carlo simulation online — nothing to install
The tool is a web application: it works in any modern browser on desktop or mobile. Your inputs are sent over HTTPS to run the simulation and aren't retained. There is no spreadsheet to download, no software to install, and no account to create.
The full model — path generation, correlation handling, cash-flow and tax conventions, and the Sobol sampling details — is documented openly on the methodology page.
Beyond the free simulation
The free tier covers the complete simulation with tax-aware modeling. A one-time QuantCalc PRO license adds the portfolio optimizer, PDF report export, and side-by-side comparison across the published forecast sources — see plans and pricing.