The equation for EVA shows that there are three key components to a company's EVA: NOPAT, the amount of capital invested and the WACC. NOPAT can be calculated manually but is normally listed in a public company's financials. Capital invested is the amount of money used to fund a specific project. WACC is the average rate of return a company expects to pay its investors; the weights are derived as a fraction of each financial source in a company's capital structure. WACC can also be calculated but is normally provided as public record.
Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.