The CET1 ratio compares a bank's capital against its assets. The Tier 1 capital ratio can be expressed as all of a bank's core capital or as the Tier 1 common capital ratio or CET1 ratio. CET1 ratio compares a bank's capital against its risk-weighted assets to determine its ability to withstand financial distress. Tier 1 common capital ratio: Also known as the common equity Tier 1 ratio, or CET1 ratio, this excludes preferred shares and non-controlling. Tier 1 capital is the core measure of a bank's financial strength from a regulator's point of view. A mandatory "capital conservation buffer", equivalent to 2.