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Excel Basics · Interactive lesson 4 of 12

Basic formulas

A formula always starts with an equals sign. It can reference other cells instead of typed-in numbers, so the result updates automatically whenever the underlying data changes.

BeginnerInteractive

Screens shown: Excel for Microsoft 365 for Windows. Practice works in any browser.

Written tutorialHow to Write Basic Formulas in Excel

Skill check

Try these first:

  • Write a formula that adds two cells together.
  • Write formulas for subtraction, multiplication, and division between cells.
  • Explain why =A2+B2 updates automatically but typing 15 doesn't.

All familiar? Skip ahead to M5 — Essential Functions.

Teach

What you're learning

=
Starts every formula — without it, Excel just stores what you typed as plain text.
Addition
=A2+B2
Subtraction
=A2-B2
Multiplication
=A2*B2
Division
=A2/B2
Tip: click a cell instead of typing its address while building a formula — Excel drops the reference in for you, and it can't be misspelled.

Where to find it in Excel

Any cell›Type =›Formula bar

Swipe sideways to see the whole window.

  1. 1Click the cell for the result and type = to start a formula.
  2. 2The cell shows the answer; the formula bar shows the formula behind it.
  3. 3#DIV/0! means a formula tried to divide by zero or an empty cell.

Rendered view of Excel for Microsoft 365 (Windows). Ribbon layout can differ slightly on Mac, Excel for the web or a narrow window.

Guided practice

A small receipt — four dashed cells, one for each operator. Work through them in order.

🧾 Receipt — click a dashed cell
—
ƒx
Start with Line Total — multiply Price × Qty.

When a formula goes wrong

#DIV/0!
The formula divides by zero — or by a cell that's currently empty.
#VALUE!
One of the ingredients is the wrong type — often text where a number was expected.
#####
Not an error — the column is just too narrow to display the result. Widen it (M2).

Real-world exercise

Item, price, quantity, total

Build a small table with columns for Item, Price, Quantity, and Total. Enter =B2*C2 in the first Total cell, then get the same formula into every row below it — you'll see exactly how in the next module.

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