Most Backtest Calculators Ignore the Portfolio You Already Have
Most backtest calculators answer a narrow question: what would $10,000 in a single ticker have returned since some date? That is useful in isolation, but it ignores the portfolio you actually hold. Adding a concentrated tech stock to a portfolio that is already 40% technology behaves differently than adding it to a diversified one.
Guardfolio's backtest simulator starts from your real, connected holdings. Pick up to five stocks, ETFs, or mutual funds and a dollar amount for each, and the simulator rebuilds two versions of your portfolio, one with today's weights and one with the hypothetical purchase folded in, then replays both across the same market history.
Built from your real holdings, not a hypothetical portfolio
Generic calculators simulate a single position in isolation. Guardfolio's backtest scales your simulated purchase into your actual current allocation, based on your top 20 direct holdings, so the before-and-after comparison reflects the portfolio you actually have.
How the Backtest Simulator Works
Before vs. after comparison
See total return, CAGR, max drawdown, and volatility for your current portfolio side by side with the portfolio you would have after the simulated purchase.
Growth of $100 chart
A single chart plots both portfolios over the same lookback window, so the divergence is visible day by day, not just in the summary numbers.
2 or 5 year lookback
Toggle between a 2-year and 5-year window to see whether the impact of the purchase holds up across different market conditions.
Monthly rebalancing assumption
Both portfolios are rebalanced to their target weights every month, so the comparison isolates the effect of the purchase rather than ordinary portfolio drift.
Nothing is added until you decide
Running a backtest is explicitly opt-in. It is a hypothetical illustration, no shares are bought and nothing changes in your real portfolio.
Built on your connected accounts
The simulation draws on your top 20 direct holdings across connected, synced accounts, the same data Guardfolio uses for its other portfolio risk metrics.
Who Runs a Backtest Before Buying
Before adding a new position
Considering a new stock or ETF? Simulate the purchase amount and see how it would have shifted your portfolio's return and drawdown profile over the past 2 to 5 years.
Before increasing a concentrated holding
Adding to a position you already hold a lot of can change your risk by more than the dollar amount suggests. Backtest it against your real weights before deciding.
Before rotating into a new sector or theme
Simulate a purchase in a sector you do not currently hold to see how it would have affected volatility and drawdown alongside your existing mix.
What the Backtest Shows, and What It Doesn't
In the interest of setting accurate expectations, here is the current scope of the tool:
| Included today | Not part of this tool (yet) |
|---|---|
| Total return, CAGR, max drawdown, and volatility, before vs. after | Comparison against a market benchmark such as the S&P 500 |
| 2-year and 5-year lookback windows | Custom rebalancing schedules or trading rules |
| Growth of $100 chart | Sharpe ratio or other risk-adjusted return metrics |
| Hypothetical purchases (What-If Buy) | Backtesting a hypothetical sale (Sell currently shows portfolio impact only, not a historical backtest) |
| Daily closes from your top 20 direct holdings | Full ETF look-through into underlying fund holdings |
For dedicated strategy research, custom rebalancing rules, or benchmark-relative backtesting, a platform built specifically for that job is a better fit; see how Guardfolio compares to Portfolio Visualizer. Guardfolio's backtest is built to answer one focused question fast: how would this specific purchase have changed the portfolio you already have?
Methodology: both portfolios use fixed weights rebalanced monthly; cash is assumed to earn 0%; returns are calculated in each asset's local currency; the simulation uses daily closes from your top 20 direct holdings, the same data source as Guardfolio's other portfolio risk metrics.
See It on Your Own Portfolio
Connect your accounts and run a backtest on a real purchase you are considering.
Start Free TrialBacktest Simulator Questions
What is Guardfolio's portfolio backtest simulator?
It is a feature inside Guardfolio's What-If Simulator that replays a hypothetical stock, ETF, or mutual fund purchase across your real connected portfolio. It compares total return, CAGR, max drawdown, and volatility for your portfolio before and after the simulated purchase, over a 2 or 5 year window.
How is this different from Portfolio Visualizer or other backtest calculators?
Generic backtest calculators typically test one ticker or a hypothetical model portfolio in isolation. Guardfolio's backtest starts from your actual connected holdings and shows how a purchase would change the portfolio you already hold. It does not replace dedicated research platforms for custom trading rules, multiple rebalancing schedules, or benchmark-relative analysis.
Can I backtest selling a position?
Not yet. Guardfolio's What-If Simulator currently shows the immediate portfolio impact of a hypothetical sale. Historical backtesting is available for hypothetical purchases only.
What data does the backtest use?
The simulation uses daily closing prices for your top 20 direct holdings in a connected, synced portfolio, the same market data Guardfolio uses for its other portfolio risk metrics. It does not look through ETF holdings to their underlying constituents.
Does running a backtest change my real portfolio?
No. Running a backtest is explicitly user-triggered and never adds a position, places a trade, or changes a connected account. It produces a hypothetical illustration only.
Is the backtest simulator free to use?
The backtest simulator is available to signed-in users with a connected portfolio as part of Guardfolio's free trial. It is currently in beta, so availability and scope may change as the feature is refined.
Guardfolio is an informational monitoring tool. It does not provide personalized investment advice. Past performance does not guarantee future results. Backtest results are a hypothetical illustration based on historical data and do not predict how any purchase would perform in the future.