Stock correlation calculator

Pearson correlation between two return series — the one-number answer to "do these two things actually diversify each other?" Runs in your browser; nothing is sent or stored.

Series A — periodic returns in % (commas, spaces, or one per line) Series B — same periods, same order

Reading the number

+1.0 — they move in lockstep; no diversification.
~+0.7 and above — largely the same bet wearing two tickers.
~0 — genuinely independent movement.
Negative — one tends to rise when the other falls; true hedging behaviour, and rare among equities.

The caveat that matters most

Correlations are regime-dependent, and they converge toward 1 in a crisis — the moment you most need diversification is the moment historical correlation is least reliable. A calm-period correlation of 0.3 between two cyclical stocks tells you little about how they'll behave the week a chokepoint closes. That regime problem is a large part of why Farlens maps event exposure rather than relying on historical co-movement alone.

Statistical limits: Pearson r measures linear association only, and short series produce unstable estimates — below ~30 observations, treat the number as a sketch.