How to Benchmark Your Portfolio Against SPY

Benchmarking your portfolio against SPY is one of the most valuable things you can do as an active investor. It's also one of the most frequently done wrong.

Here's the correct methodology — and the shortcuts that make comparisons misleading.

The Goal of Benchmarking

The purpose of benchmarking isn't to feel good or bad about your returns. It's to answer: given what I could have done (buy SPY and do nothing), was my active management worth it?

"Worth it" means beating the passive alternative on a risk-adjusted basis. Raw return comparison is a starting point, but not the finish line.

Step 1: Choose the Right Start Date

Both series must start from the same date. This sounds obvious but is frequently violated.

If you started trading in March 2023, your benchmark should also start in March 2023 — not January 2023, not some earlier date. SPY's cumulative return from March 2023 is what an investor who chose the passive option at the same time you chose the active option would have gotten.

Using a different start date for the benchmark can create artificial gaps that have nothing to do with your strategy's performance.

Step 2: Use the Same Return Methodology

Both your portfolio return and the benchmark return should be calculated as total return (dividends reinvested) using the same time-weighting methodology.

SPY's published performance figures are total return, dividend-adjusted. This is equivalent to a TWR for a fully passive investor.

Your portfolio return should also be time-weighted — adjusted to remove the effect of your deposits and withdrawals. If you compare your IRR (money-weighted) to SPY's total return, the comparison is invalid: you might show higher returns simply because you added capital before a strong month.

Step 3: Normalize to the Same Baseline

Plot both series starting from 0% (or 1.0 as a cumulative index) at the start date. This makes the visual comparison clear: at any given point in time, the gap between the two lines is your alpha or deficit relative to the benchmark.

Some analytics tools plot portfolio value in dollars and SPY value in some separate format. This is confusing and should be avoided. Both lines should be percentage return from the same baseline.

Step 4: Account for Risk

Here's where most comparisons stop being honest.

If SPY returned 18% and you returned 24%, you outperformed by 6 percentage points. But if your maximum drawdown was 28% vs SPY's 14%, you took twice the downside risk. Whether the extra return is "worth it" depends on whether 6% of extra return justifies 14% of extra drawdown.

The Calmar ratio captures this directly: return / max drawdown. If your Calmar ratio is lower than SPY's equivalent (roughly 0.5 over long periods), you underperformed on a risk-adjusted basis even if your absolute return was higher.

Similarly, if your Sharpe ratio is below SPY's historical ~0.5, your strategy isn't generating efficient risk-adjusted return.

Step 5: Look at the Correlation and Beta

Two portfolios can have identical cumulative returns but very different characters:

• One tracks SPY closely (high correlation, beta near 1) — essentially paying active management costs for index-like returns
• One has low correlation to SPY — potentially genuine diversification or an uncorrelated alpha source

Beta tells you how much your portfolio moves per 1% SPY move. A beta of 1.2 means you're taking 20% more market exposure than a SPY holder. A beta of 0.4 means you have significant non-market exposure (either hedged, or in uncorrelated assets).

If your beta is 1.5 and you beat SPY by 5%, adjusting for beta you might actually be underperforming a leveraged index exposure.

The Full Checklist

Beyond SPY: When to Use Other Benchmarks

SPY is appropriate for most equity portfolios. But if your strategy is concentrated in a specific sector or style, a more specific benchmark is fairer:

• Tech-heavy portfolio: QQQ (NASDAQ 100)
• Small-cap strategy: IWM (Russell 2000)
• International exposure: EFA or VEA
• Sector strategy: The relevant sector ETF (XLK, XLE, etc.)

Using SPY as your benchmark when your portfolio is 80% in semiconductors will make you look great in tech bull markets and terrible in sector rotations — neither comparison tells you much about your stock-picking ability within the sector.

How AlphaLens Handles Benchmarking

AlphaLens fetches the benchmark series for the same date range as your account history and normalizes both to start at 0%. The benchmark is selectable from the controls row — SPY, QQQ, IWM, and others.

For multi-account portfolios, each account gets its own benchmark series starting from that account's inception date, so performance comparisons are always on equal footing.

Connect your broker to see your portfolio benchmarked correctly.