Section: Formulas
...Subsection: Some things to notice about formulas

The formula character

Don't forget that the formula character appears exactly once, that it flags the cell as containing a formula, and that it has no effect on anything else.

Cell value vs. cell appearance

This topic came up before when talking about dates; the text that appears in a cell isn't necessarily the same as the actual underlying value. With formulas, the underlying value is the formula. What appears on the screen depends on the result of the formula and how you have the cell set up to display numbers and text.

Most of the time you will see the RESULTS of the formulas, not the formulas themselves. In the examples later on, we will show you the formulas so you can see what is happening. This diagram might help: Both sides are looking at EXACTLY the same spreadsheet. The only difference is that the results are shown in the left-hand example, and the formulas themselves are shown on the right.

Updates happen instantly

If your formula references other cells, changing the value of a referenced cell immediately results in a change in the cell with the formula. There's no waiting involved; things just go!

Order of operations counts!

Don't forget about order of operations; anything inside parenthesis happens first, followed by multiplication and division, followed by addition and subtraction. When in doubt, use parenthesis to say exactly what you mean. Better safe than sorry.

Empty cells and text cells have a value of zero

Any cell that has nothing in it or has just a string in it has a numeric value of zero. Sometimes your formulas will seem to work but come up with the wrong data -- check to make sure you aren't referencing any empty cells. It can also be useful: if you don't know how long a column is (because you keep adding data to it) you can feel comfortable using a formula like "=sum(A5:A10000)" and know it will come up with a good answer and not freak out.