The Price-to-Earnings Ratio or P/E ratio is a ratio for valuing a company that measures its current share price relative to its per-share earnings.The price-earnings ratio can be calculated as: Market Value per Share / Earnings per Share.For example, suppose that a company is currently trading at $43 a share and its earnings over the last 12 months were $1.95 per share. The P/E ratio for the stock could then be calculated as 43/1.95, or 22.05.he price-to-earnings (P/E) ratio is calculated by dividing a company’s stock price per share by its earnings per share (EPS), ...