Bank capital is the layer of a bank’s funding that absorbs losses before depositors and other creditors are touched: mostly shareholders’ equity and retained profits. It is not cash in a vault but a claim structure, and its size relative to the bank’s risk determines how much bad news the institution can take before it is in trouble. Nearly every post-2008 banking rule is, at bottom, an argument about this number.
The ratios that matter
The headline measure is the CET1 ratio: common equity tier 1 capital divided by risk-weighted assets, which scale each loan and security by its riskiness. Regulators set minimums plus buffers, and large US banks receive an additional firm-specific requirement from the Federal Reserve’s annual stress tests, which simulate a severe recession and measure how far capital would fall. A bank’s distance above its requirement is its room for buybacks, dividends and growth.
Why equity investors watch it
Capital is the gate on shareholder returns: buybacks and dividend rises are only permitted from the surplus above requirements, so stress-test results and rule changes translate directly into payout capacity. Capital requirements also shape behaviour, pushing banks away from assets with heavy risk weights, which is one reason lending has migrated toward private credit funds outside the banking rulebook.
The recurring debate
More capital makes banks safer but constrains lending and returns; less does the opposite. Every loosening is greeted as stimulus for credit and bank shares, every tightening as a drag, and the cycle of reform and rollback tends to follow the distance from the last crisis. When bank stocks move on a regulatory headline, this is the mechanism.
Where you’ll meet this in our coverage
Wall Street’s Record Quarter: Why Goldman Soared and Citi Fell on the Same Day