The correlation between Bitcoin (BTC) and Ethereum (ETH)

The correlation between Bitcoin (BTC) and Ethereum (ETH) is structurally high and stable, typically ranging between +0.80 and +0.90 across various time horizons, with 30-day figures around +0.88 and one-year values between +0.82 and +0.91. This relationship is markedly different from the BTC-Gold correlation, which averages only about +0.10 to +0.13 and can sometimes be negative.

BTC and ETH essentially behave as two expressions of the same underlying crypto risk factor, driven primarily by global liquidity and market sentiment, with only periodic tactical divergences caused by Ethereum-specific catalysts such as ETF flows, staking yields, Layer-2 activity, and DeFi narratives. The observed correlation levels in 2026 remain consistently high, with the 30-day correlation at +0.88, 90-day figures around +0.90 to +0.94, and a long-term baseline of approximately +0.81 to +0.85. Significant decoupling events are rare and typically short-lived. The main drivers of co-movement include shared exposure to global crypto liquidity, institutional flows, risk-on/risk-off sentiment, and common dependency on ETF and stablecoin dynamics.

Divergence factors include Ethereum-specific catalysts, rotation cycles reflected in the ETH/BTC ratio, and differences in volatility, with ETH generally being more volatile than BTC. The ETH/BTC ratio, which measures relative performance between the two assets, followed a downward trend from August 2025 through mid-2026. However, in July 2026, this ratio broke above a descending channel and stabilized around 0.029 to 0.030, signaling a potential rotation shift. While this is not yet a confirmation of an “alt season,” it represents the clearest technical signal in nearly a year.

For portfolio construction, the high correlation implies only modest diversification benefits from holding both BTC and ETH together. The combined exposure effectively behaves like a single crypto factor with implicit leverage on ETH. To reduce concentration risk, investors are better served by adding assets with low correlation to crypto, such as physical gold, cash, or certain traditional assets, rather than increasing ETH allocation purely for diversification purposes. Key monitoring points include rolling 30-day and 90-day BTC-ETH correlations, the ETH/BTC ratio (watching channel breaks and levels at 0.025, 0.031, and 0.035), BTC vs. ETH ETF flows, Bitcoin dominance, and relative volatility between the two assets. In conclusion, the BTC-ETH correlation is high, stable, and structural, confirming that both assets share a dominant common risk factor. While tactical divergences exist and are visible in the ETH/BTC ratio, they do not undermine the fundamental relationship.

In a Markowitz or risk-parity framework, this argues for disciplined allocation between the two assets rather than naive additive exposure. The analysis could be extended further with a Markowitz simulation of BTC plus ETH, integration of this correlation into the BLSI framework, or a more detailed examination of the ETH/BTC ratio dynamics.