Market capitalization is calculated by the total number of common shares outstanding multiplied by the stock price, It does not account for options. Of the three metrics, it is the easiest to find, calculate, and understand.
Fully diluted equity is calculated as fully diluted shares outstanding multiplied by the stock price. Fully diluted shares outstanding accounts for the impact of the in-the-money options through the treasury method. It is considered the most accuarte indicator of equity value.
Shareholder’s equity represents the book value of equity investments plus any accumulated net income less any dividends paid. Equity investments are recorded at the value of the initial investment rather than their current market price. For example, if the company issues 1,000 shares at $10 / share to raise $10,000, which is recorded on the balance sheet. It does not matter if the stock price has risen to $20 / share. On the balance sheet, the company will still have $10,000 of stock, regardless of the fluctuations in market price.