Common Equity Tier 1 Ratio

A key regulatory capital ratio measuring a bank's core equity capital against its total risk-weighted assets.

The Common Equity Tier 1 (CET1) ratio is a key regulatory metric established under the international Basel III framework to evaluate a bank's financial strength and resilience against insolvency. It measures a bank's core capital—which consists primarily of common stock, retained earnings, and accumulated other comprehensive income—against its total risk-weighted assets (RWA). Risk-weighted assets are a bank's loans and other investments adjusted to reflect their relative default risk, meaning safer assets like government bonds require less capital backing than riskier commercial loans. For retail investors, the CET1 ratio is the definitive health check for a banking institution. It indicates how much of a financial cushion the bank possesses to absorb unexpected losses before it risks failure. Regulators enforce strict minimum CET1 requirements, which typically start at a baseline of 4.5% but can rise significantly higher once various capital conservation and systemic risk buffers are added, often requiring major banks to maintain ratios well above 10%. When analyzing bank stocks, a high CET1 ratio above regulatory minimums suggests a highly stable institution with the financial flexibility to fund share buybacks, increase dividends, or expand its loan portfolio. Conversely, a low or rapidly declining CET1 ratio is a major red flag. It indicates that the bank may be forced by regulators to restrict dividend payments, halt buybacks, or raise highly dilutive equity capital to restore its regulatory safety net.

Bank A has $15 billion in Common Equity Tier 1 capital (retained earnings and common stock). Its total assets are adjusted for risk, resulting in $120 billion of risk-weighted assets. Its CET1 ratio is calculated as ($15 billion / $120 billion) 100 = 12.5%.