Knowing at least 5 basic Excel formulas can be extremely helpful these days, when many workers are expected to have some basic technical skills. Spreadsheets like Excel have become an essential part of not just business but also of home finance, so it's a bit worrying that so many people do not know even the most basic Excel formulas.

1.  Sum. “Sum” is easily the most common and the most basic of Excel formulas. There are two ways the sum formula can be written: as a list of cells to be added together or as a range of cells to be added together. The first looks something like this: “=SUM(A1,A2,A3,A4)”. The list of cells can be as long as necessary, so long all the cell names are separated by commas. The other form of this basic Excel formula is by range. In this case, the following would have exactly the same effect as the previous: “=SUM(A1:A4)”. The two can even be combined; for example, “=SUM(A1:A3, A5)” will add cells A1, A2, A3 and A5, skipping A4.
2.  Product. The syntax for the “product” basic Excel formula is exactly the same as the syntax for the “sum” formula. Simply give a list or a range of values to be multiplied together.
3.  Average. The “average” basic formula, also known as the mean for those out there who like fancy words, takes the sum of all cells given to it and divides by the total number of cells. So, for example, the code “=AVERAGE(A1:A3)” takes three cells (A1, A2 and A3), adds the contents of these cells together and divides by three.
4.  Date. The “date” Excel formula is a pretty handy one. It allows you to explicitly declare that you want to store a date in a cell. The format is easy: “=DATE(2010, 3, 15)” will store the date March 15, 2010.
5.  Days360. Now that you know about the date function, you can do some neat things with it. Using the basic excel function “Days360,” you can find the amount of time that exists between two dates. Simply write “=DAYS360(A1,A2)” to find the difference between the two dates stored in cells A1 and A2.