This short note introduces all of the important and commonly used financial ratios, organized into five categories: (1) liquidity ratios, which measure a company's ability to meet short-term debt obligations; (2) leverage ratios, which evaluate a company's capital structure by measuring how a firm uses debt and equity to finance its operations; (3) efficiency ratios, which measure how efficiently a company is utilizing its assets and resources; (4) profitability ratios, which measure a company's ability to generate profit from its resources; and (5) market ratios (also called valuation ratios), which evaluate the share price of a company's stock.