Stock Correlation Matrix
See how closely a set of stocks actually move together. Enter up to eight tickers for a correlation heatmap and a diversification score — because "is NVDA just AMD?" has a real answer.
"Is NVDA just AMD?"
A portfolio can look diversified — ten different tickers — and still be one bet in a trench coat. If everything you own moves together, you have not spread your risk; you have just spread your attention. Correlation is how you check. It measures, on a scale from +1 to −1, how closely two stocks' daily returns track each other: +1 is near-lockstep, 0 is unrelated, −1 is mirror opposites. Two holdings correlated at 0.9 give you almost no diversification versus owning either one alone.
The diversification scoreboils the whole matrix down to a single 0–100 number: 100 would mean your holdings perfectly hedge each other, 50 means they are effectively unrelated, and a low score means they are largely the same bet. It is the fast answer to "am I actually diversified, or does it just look that way?"
How it works
We take each stock's end-of-day closing prices over your chosen window, turn them into daily returns, and compute the Pearson correlation of those returns for every pair — the standard measure. The result is a heatmap (greener = more correlated, redder = more inversely correlated) plus the single diversification score. A correlation is a derived statistic, not a live quote.
Two honest caveats. First, our closing prices are unadjusted, so a stock split would otherwise show up as a fake ±90% day — we filter those split-day artifacts out before computing. Second, and more important: correlation is backward-looking and drifts, especially in a crisis, when normally-independent things tend to fall together at exactly the wrong moment. Treat this as a snapshot of the recent past, not a guarantee about the future. Educational only, not financial advice.
Keep going
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Common questions
What does stock correlation tell me?
Correlation measures how closely two stocks move together, on a scale from +1 to −1. +1 means they rise and fall in near-lockstep; 0 means their day-to-day moves are unrelated; −1 means they mirror each other. Two holdings with a correlation near +1 give you little diversification — you effectively own more of the same bet.
What is a good correlation for diversification?
Lower is better for diversification. Holdings correlated above ~0.8 behave almost identically, so adding the second one barely reduces your risk. Correlations near 0 (or negative) genuinely spread risk, because a bad day for one is not automatically a bad day for the other. The diversification score summarizes this across all your pairs.
What data is this based on?
Pearson correlation of daily returns computed from our end-of-day closing prices over the window you choose (6 months, 1 year, or 2 years). It is a derived statistic, not a live quote. Split-day price artifacts are filtered out so a stock split does not show up as a fake correlation.
Does correlation stay the same over time?
No — and that is the most important caveat. Correlations drift, and they tend to spike toward +1 in a crisis: in a sharp market-wide selloff, things that normally look independent often fall together, exactly when you were counting on them not to. Treat these numbers as a backward-looking snapshot, not a promise.