Writing your first formulas

=5+2*3 gives 11, not 21. Microsoft's operator table says multiplication comes before addition.

The equals sign

A formula is an instruction that the spreadsheet carries out and replaces with its answer. It always begins with an equals sign. Type =3+4 and the cell shows 7; type 3+4 without the sign and the cell holds the text 3+4. Microsoft's help puts it this way: the equal sign tells Excel that the characters that follow make up a formula. After the sign come operands, the numbers and cell references, joined by operators such as + and *.

Which part is worked out first

When a formula mixes operators, Excel follows a fixed order. Microsoft lists it from first to last: negation (as in −1), percent, exponent, multiplication and division, addition and subtraction, joining text with &, and finally comparisons. Operators on the same level go from left to right. So =5+2*3 multiplies first and gives 11, while =(5+2)*3 adds first because of the brackets and gives 21. Brackets are the tool for getting the order you mean, and extra brackets never hurt.

One result surprises people who know school algebra. Because negation comes before the exponent in Excel's list, =-2^2 means (−2) squared and gives 4, not −4. If you want minus two squared, write =-(2^2). It is a good example of why a formula that matters should be checked with a value you can work out in your head.

Point at cells instead of typing numbers

A formula such as =3.5*4 works, but it hides the numbers inside the formula. Put the price in B2 and the quantity in C2, and write =B2*C2 in D2 instead. Now the inputs are visible, and when you change the quantity in C2 the cost in D2 updates by itself. This is the main reason spreadsheets exist. You do not have to type the address: while you are writing a formula, click a cell and its address is inserted at the cursor, and dragging across cells inserts a range.

Function and cell names are not case-sensitive, so =b2*c2 works and is shown in capitals. Text inside a formula must be in double quotes, as in ="Total: "&D4. Without the quotes, the program looks for a name called Total, finds none, and shows #NAME?. In the lab, the panel under the grid lists every cell a formula uses, in the same colour as its outline in the grid, which makes it easy to see whether a formula points where you think it does.

Editing works the same way in both programs. Select the cell and click into the formula bar, or double-click the cell, change the formula and press Enter to keep it or Escape to throw the change away. Typing straight into a selected cell replaces what was there, which is a common way to lose a formula by accident. If a result looks wrong, check it with numbers you can do in your head: put 10 and 2 in the input cells, predict the answer, and see whether the formula agrees before you trust it with real figures.