Lesson 3.1 – How Formulas Work
Formulas are the core of Excel. They allow you to perform calculations, analyze data, and automate tasks. Every formula in Excel follows a simple structure and always begins with an equal sign (=). Understanding how formulas work is essential before learning specific functions.
1. The Structure of a Formula
All Excel formulas follow this basic pattern:
=operand operator operand
Example:
- =5 + 3
- =A1 * B1
- =SUM(A1:A10)
Excel calculates the result and displays it in the cell, while the formula remains visible in the Formula Bar.
2. The Equal Sign (=)
Every formula must start with =. Without it, Excel treats the entry as text.
Examples:
- =10+5 → Excel calculates
- 10+5 → Excel shows “10+5” as text
3. Operators in Excel
Operators tell Excel what type of calculation to perform.
| Operator | Meaning | Example |
|---|---|---|
| + | Addition | =A1 + B1 |
| - | Subtraction | =A1 - B1 |
| * | Multiplication | =A1 * B1 |
| / | Division | =A1 / B1 |
| ^ | Exponent | =A1 ^ 2 |
4. Order of Operations (PEMDAS)
Excel follows a specific order when calculating formulas:
- Parentheses
- Exponents
- Multiplication and Division
- Addition and Subtraction
Example:
=2 + 3 * 4
Excel calculates 3 * 4 first → result = 14 To force addition first:
=(2 + 3) * 4
Result = 20
5. Cell References
Instead of typing numbers directly, formulas usually refer to cells.
Examples:
- =A1 + B1
- =A2 * 10
- =SUM(A1:A10)
This makes formulas dynamic — if the cell value changes, the formula updates automatically.
6. Formula Errors
Excel displays error codes when something goes wrong.
| Error | Meaning |
|---|---|
| #DIV/0! | Division by zero |
| #VALUE! | Wrong data type |
| #NAME? | Misspelled function |
| #REF! | Invalid cell reference |
7. Practical Exercise
Practice basic formulas with the following steps:
- Create a worksheet named Lesson_3_1_Practice.
- Enter numbers in cells A1, A2, A3.
- Create formulas for addition, subtraction, multiplication, and division.
- Use parentheses to change the order of operations.
- Experiment with cell references instead of typing numbers.
- Trigger and fix a #DIV/0! error.
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