Inputs and settings

The setup panel is a four-step column on the left of the Monte Carlo tool. This page documents every control across the four steps, with its accepted values, default, and what it changes, plus the validation gates that must pass before you can run. The tool is available to Free, Pro Lite, and Pro accounts; some sources are limited to Pro.

Before you begin

Sign in to your account. The tool is available to Free, Pro Lite, and Pro.
Open the Monte Carlo tool. The four-step setup panel appears on the left.
Personal, model, and combined portfolio sources require a portfolio you own. To build one, see Build your first portfolio.

What it shows

The setup panel collects everything a run needs. The four steps move from what to simulate, through naming and capital, to horizon and scenario, and finally to optional advanced settings. The sections below describe each step in order.

Inputs

Step 1: Pick what to simulate

This step chooses the basket and the allocation.

Portfolio Source (dropdown). The options are:
- My Portfolios: one of your own saved portfolios. Its current holdings and weights load automatically. Restricted to Pro and higher; shown locked with a "Pro+" note on lower tiers.
- Model Portfolios: a pre-built strategy portfolio. Restricted to Pro and higher; shown locked on lower tiers.
- Combined Portfolios: several of your own portfolios merged into one basket, selected with checkboxes. Populated from your own portfolios.
- Custom Stocks: a basket you build by searching and adding tickers. Available to every tier, and the default working mode for Free and Pro Lite.
Custom Stocks search (Custom mode only). Type or paste tickers, single or comma-separated. A counter shows how many of your tier's ticker limit you have used. Adding past the limit is blocked with a notice.
Combined selection (Combined mode only). Checkboxes for each of your portfolios, with a count of how many of how many you have selected.
Allocation weights (appears once a source has holdings):
- Equal weights (default): capital is split evenly across all holdings.
- Custom weights: open the weights editor to set each holding's percentage. Weights must total 100.00 percent or the run is blocked. Selecting a personal or model portfolio loads that portfolio's actual allocations as custom weights.

Step 2: Name and starting capital

This step labels the run and sets the dollar value the projection starts from.

Simulation name (text, optional). Free text used to label the run in History. If left blank, an automatic name with today's date is used. Duplicate names are auto-numbered with a suffix such as "(1)".
Starting capital (mode selector):
- Custom amount (default): a dollar figure you type. The default value is a round starting figure. It must be greater than 0.
- Current value: the present market value of the selected portfolio, computed from the latest prices. Available when a personal or combined portfolio is loaded.

Step 3: Horizon and scenario

This step sets how far the projection runs, which market regime it models, and how many paths it generates.

Time Horizon (dropdown). Accepted values: 1 Week, 2 Weeks, 3 Weeks, 1 Month, 3 Months, 6 Months, 9 Months, 1 Year, 2 Years, 3 Years, 5 Years, 7 Years, 10 Years. Default: 5 Years. This sets how far forward the simulation projects.
Risk Scenario (dropdown). Accepted values: 2008 Crisis, Conservative, Current Conditions, Optimistic, Bull Market. Default: Current Conditions, the baseline that uses your stocks' measured history as is. Each scenario scales the estimated return and volatility before simulating, to model different market regimes. The crisis scenario additionally draws from a heavier-tailed distribution to model shocks.
Simulation Quality (dropdown). Accepted values and run sizes:
- Quick: 5,000 paths, about 8 seconds.
- Standard: 10,000 paths, about 15 seconds. This is the default.
- Premium: 50,000 paths, about 90 seconds.
- Expert: 100,000 paths, about 3 minutes.
- More paths give steadier percentile estimates at the cost of a longer wait.

Step 4: Advanced (optional)

This step is optional. The defaults produce a sound run, so you can skip the whole step.

Return Model (dropdown). Historical (default, uses your stocks' actual past returns) or Custom. Historical is recommended.
Lookback Period (number, trading days). How much past data is used to estimate each stock's return and volatility. Default 4,500 days (about 18 years). Minimum 252 (1 year), maximum 5,040 (about 20 years), in steps of 252. A helper line shows the equivalent in years. Runs below 252 days are blocked.
Rebalancing (dropdown). Never (default), Monthly, Quarterly, Semi-Annual, Annual. How often the simulated portfolio is traded back to its target weights.
Dividend Reinvestment (checkbox). Enabled (default) reinvests dividends into more shares; Disabled treats them as cash.

Cash flow schedule

These controls add deposits or withdrawals on a cadence across the horizon.

Cash Flow Type (dropdown): None (default), Contributions (add money), Withdrawals (remove money).
Amount Type (dropdown, when a cash flow is set): Flat Dollar Amount or Percentage of Portfolio. Percentage scales with the portfolio's value each period, which is common for withdrawal rules.
Amount per period (number): a dollar figure for flat, or a percent (0 to 100) for percentage.
Frequency (dropdown): Monthly, Quarterly, Semi-Annual, Annual.
Adjust for inflation (checkbox, flat amounts only). When on, the contribution grows each year by the Annual Inflation Rate (number, default 2 percent, accepted range minus 10 to plus 20 percent).

Goal-based planning

This control adds a target value so results report your chance of reaching it.

Set target portfolio value (checkbox). When on, enter a Target Portfolio Value in dollars. Results then report the probability of reaching it.

Transaction costs

These costs apply only during rebalancing trades. The panel surfaces them once a cost is non-zero.

Commission per Trade (dollars, default 0).
Slippage (percent, default 0, accepted up to 5 in this field). Slippage nudges buy prices up and sell prices down.
Dividend Tax (percent, default 0, accepted 0 to 50). Applies to dividend income.
If Rebalancing is Never and you set a cost above 0, a notice explains that costs apply only during rebalancing trades. Set a rebalancing cadence or return the cost to 0.

Outputs and how to read them

The setup panel produces no figures of its own. It assembles the configuration that the run uses, then hands off to the results report. For the figures the run produces, see Results and metrics.

How it is calculated

The Lookback Period directly governs the inputs the model measures, so it is worth understanding before you change it. A longer lookback averages over more market conditions and steadies the estimates of return and volatility. A shorter lookback reacts faster to recent behavior but is noisier. The default of about 18 years spans several full market cycles. For the full method that turns these inputs into a projection, see How it works.

Data and timing

The simulation runs on daily split-and-dividend-adjusted closing prices. Market data comes from AlphaVantage, with Nasdaq-listed quotes delivered through AlphaVantage. Prices refresh each trading day after the close, so each run uses history through the most recent completed trading day.

Use cases

Build a custom basket and split capital evenly to compare a few candidates at once.
Load a saved portfolio at its current market value to project where it could go next.
Model a withdrawal rule by setting a percentage-of-portfolio cash flow on an annual cadence.
Set a savings target with monthly contributions to read your chance of reaching the goal.

Limitations and disclosures

The inputs set the assumptions, not the future. A longer lookback does not guarantee a more accurate projection if the market regime changes, and short price histories produce less reliable estimates, which the Holdings table flags. The configuration here drives a modeled projection, not a guarantee of results.

GNG Research provides equity research and educational tools, not investment advice. Nothing on the platform is a recommendation to buy or sell any security. Do your own research and consider your circumstances before making any investment decision.