profit % can be calculated by the help of following formula:-
The difference between selling price and cost price of an article is the profit.
Divide profit by the cost price, and multiply this by 100 to get profit percentage on that article. Thus,
Profit percentage=(Selling Price-Cost Price)*100/Cost Price
Suppose an apple vendor has purchased an apple at 46p (this is the C.P.) and sells it at 50 p, the profit made on the apple is (50-46)=4p
Hence profit percentage=4*100/46=8.7
If however, for some reason he has to sell it at 40p, his profit would be (40-46)=-6p
Profit percentage, then=-6*100/46=-13.0
Negative value of the result indicates an actual loss, in the last instance.