how we calculate ROI?

Return on investment (ROI) is the concept of an investment of some resource yielding a benefit to the investor.
As a performance measure, it is used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments.
In purely economic terms, it is one way of considering profits in relation to capital invested.
return on investment (%) = Net profit / Investment ×100 or return on investment = (gain from investment - cost of investment) / cost of investment[1]

ROI stands for Return On Investment, and it equals the net income divided by the average investment