Portfolio Monte Carlo Lab
Run seeded scenario simulations using editable return, volatility, contribution and withdrawal assumptions.
How to use this Portfolio Monte Carlo Lab
Monte Carlo analysis answers a different question from a deterministic calculator. Instead of showing one compound return path, it generates many paths from a stated return-and-volatility model and summarizes the distribution of ending corpus values. The Finin2min implementation is seeded for reproducibility: the same assumptions and seed generate the same diagnostic output.
Calculation logic
The rigorous engine uses monthly lognormal return draws derived from the entered annual mean and volatility assumptions. A lognormal gross-return process cannot generate a monthly loss below -100%. Contributions and withdrawals are applied monthly, and withdrawals can grow with inflation. The output reports corpus-survival frequency plus the 10th percentile, median and 90th percentile ending corpus across simulations.
Worked interpretation
A 70% simulated success rate means 70% of the generated paths under the chosen model finish above zero. It does not mean the investor has a 70% real-world chance of success. Changing volatility while holding average return constant can materially change downside percentiles, which is exactly why a distribution view is useful.
What this result does not prove
Simulation probability is model probability, not real-world certainty. Market returns are not guaranteed to be lognormal, independent or stationary; correlations, valuation regimes, fees, taxes and asset-allocation changes can matter. The tool must therefore display assumptions next to the result and should not translate a simulated success rate into a suitability recommendation.
Methodology, data and limitations
This Finin2min tool separates calculation from recommendation. Inputs, return assumptions and stress parameters remain visible and editable. Results are educational scenarios, not forecasts or suitability advice.
Primary / official references
Questions & answers
What does the Portfolio Monte Carlo Lab calculate?
Monte Carlo analysis answers a different question from a deterministic calculator. Instead of showing one compound return path, it generates many paths from a stated return-and-volatility model and summarizes the distribution of ending corpus values. The Finin2min implementation is seeded for reproducibility: the same assumptions and seed generate the same diagnostic output.
What assumptions drive the result?
The rigorous engine uses monthly lognormal return draws derived from the entered annual mean and volatility assumptions. A lognormal gross-return process cannot generate a monthly loss below -100%. Contributions and withdrawals are applied monthly, and withdrawals can grow with inflation. The output reports corpus-survival frequency plus the 10th percentile, median and 90th percentile ending corpus across simulations.
Can I treat the result as a forecast or recommendation?
No. The output is an educational scenario generated from the values entered. It does not predict market returns, recommend a security or establish suitability for an individual investor.
How should I handle market or mutual-fund data?
Use a current, complete dataset with a recorded effective date. Where the page requires imported scheme, NAV, TER, portfolio or industry data, Finin2min should publish or retain the source authority, retrieval date, parser version and file hash.
What are the main limitations?
Simulation probability is model probability, not real-world certainty. Market returns are not guaranteed to be lognormal, independent or stationary; correlations, valuation regimes, fees, taxes and asset-allocation changes can matter. The tool must therefore display assumptions next to the result and should not translate a simulated success rate into a suitability recommendation.