Many people land on my institutional site by looking for percentage calculation with Excel. And their needs, as resulting from their search keys, are rather simple to satisfy.
Therefore, I try to collect here some examples related the most common requests.
For each example, I propose a screenshot (public domain pictures, made by myself): the formula is highlighted in the formula bar.
Example 0 – (quickly, for those who really do not mean to think about it) should I want to calculate a given percentage of an amount, I can simply write a formula that multiplies the amount by the percentage. For instance I want to know the 19% of 2500, I set the cursor on a cell and write =2500*19% (or =2500*19/100; or simply =2500*19 and then I format the cell using the predefined percentage format)
Example 1 – I know the price of a product and I know that a certain discount has been applied (in the example: 15%): how much is the discount?
Example 2 – I know the price of a product and I know that I will benefit from a certain discount (in the example: 15%): how much will I spend?
Example 3 – I know the sale price of a product and I know its original retail price: what discount has been applied?
Example 4 – I know the cost of a product and I want to increase it by a certain percentage (in the example: 15%): what will be the final price?
Example 5 – I correctly answered a certain number of questions on a test (27 out of 40): how can I express this result as a percentage score?
Example 6 – How to deduct tax from a price which includes tax: I know the price of a product (gross price) and I know that a certain tax has been applied (in the example: 15%): how much is the price before tax (net price)?
Example 7 – political elections, four parties got valid votes, I know their votes and the total of valid votes, how do I calculate the percentage of each party? [in this case I have not multiplied by 100, the cell format did the dirty work; note the $ sign, to allow to copy and paste the formula]
P.S.: when I say Excel, I mean Calc as well; and also those bizarre versions of Excel that I regularly find within the log files of my sites, and which are used as search keys, such as Exel, Exell, Exelle, Excell, Excelle, Exelles, Excelles, …