CSC 110: Introduction to Computers
Learning Unit 7: Mini-Lecture
Microsoft Excel: Working with Formulas
Understanding formulas can be a little daunting, especially for those who aren’t comfortable with math.
The good news is that Microsoft Excel does a lot of the work for you. It has a large menu of specific
functions which make math calculations easy. However, you do need to understand basic math
principles in order to set up the formulas correctly.
Formula Structure:
The first thing you need to remember is that all Excel formulas begin with an equal sign (=). For example,
if you want to enter a formula for 4 plus 5, you would type this: =4+5
The equal sign tells Excel that this is going to be a mathematical calculation, rather than just a regular
text or numeric entry.
Referencing Cells:
Although you can type the numbers you want to calculate (we call them “values”) into your formula, it is
often better to use the cell reference feature instead. For example, if 4 is in cell A2 and 5 is in cell A3,
and you want cell A4 to add 4 and 5, then, instead of typing =4+5 in A4, you would use Excel’s cell
reference feature. So, if you wanted to add cells A2 and A3, and put the sum in cell A4, you would start
by clicking on cell A4. Next, type the equal sign, then click cell A2, which contains the value 4. Next, type
the mathematical operator (in this case, the plus sign for addition). Then, click cell A3, which contains
the value 5. Press the “Enter” key on your keyboard. Then, a 9 will appear in cell A4, but the formula
=A2+A3 will appear in the formula bar, when you click cell A4.
Why is this important? Because your formula will automatically recalculate if you change the value
within cells A2 or A3. If you merely type the value into the formula, and later that value changes, you
will have to recreate the formula. But if you reference the cells, it doesn’t matter whether the values
change, the formula will stay the same and automatically recalculate based on the new values. So, if you
change A2 to 3 and A3 to 7, A4 will automatically recalculate to 10. This works for both simple and
complex calculations. Imagine how much time this can save, if you have many calculations to do!
Mathematical Operators:
The following table is from Microsoft Office 2010 Simplified, by Kate Shoup.
Let’s take a few minutes to review the mathematical operators below.
Operator
+
*
/
%
^
Operation
Addition
Subtraction
Multiplication
Division
Percentage
Exponentiation
Operator
=
<
<
>
>
<>
Page 1 of 2
Operation
Equal to
Less than
Less than or equal to
Greater than
Greater than or equal to
Not equal to
CSC 110: Introduction to Computers
Learning Unit 7: Mini-Lecture
Operator Precedence:
When you are creating a complex formula, meaning a formula that contains more than one type of
calculation, the order in which Excel performs these calculations determines the result. You may recall
from prior math courses the following acronym for remembering the order in which calculations are
performed, “Please Excuse My Dear Aunt Sally” which stands for: Parentheses, Exponents,
Multiplication, Division, Addition, and Subtraction.
Let’s look at an example of how, when creating equations, the order of operations determines the
result:
Let’s calculate the average of cells A1, B1, and C1, having the result appear in cell D1.
First, you may recall that to calculate the average (or arithmetic mean) of a group of numbers, we add
each of the values together and divide by the total number of values. Thus, the average of the values 5,
6, and 10 is 7, because 5+6+10=21 and 21 divided by 3 is 7.
Using the cell reference feature, explained earlier, you can enter the formula into cell D1.
You might thing that the correct formula would be =A1+B1+C1/3
However, that would be incorrect. Using this formula, Excel would first divide the value C1 by 3 and then
add the values of A1 and B1 to the result. So, if A1 is 5, B1 is 6, and C1 is 10, then Excel would divide 10
by 3, which would be approximately 3.3, and add 5 and 6, resulting in an answer of 14.3, which we know
to be incorrect.
Instead, we need to use parentheses to construct the correct formula. To determine the average, we
need the formula to add all of the values together first and then divide the result by the total number of
entries.
Correct Formula: =(A1+B1+C1)/3
Using this formula, Excel would first add the values in parentheses, then divide that total by 3. So, using
our earlier values, (5+6+10)/3 or 21/3, which equals 7.
Conclusion
As you can see, understanding how to reference cells and properly use mathematical operators is
essential to constructing effective and powerful time-saving formulas in Microsoft Excel.
© Indian Hills Community College
Page 2 of 2