Basic Formulas

This is the lesson where Excel stops being a glorified table and starts being a calculation engine. Formulas are instructions you write into a cell that tell Excel to compute something — a total, an average, a count, a maximum. Once a formula is in place it updates automatically whenever the data it references changes. You write it once and it works forever. This lesson covers the essential formulas every Excel user needs from day one.

How Formulas Work

Every formula in Excel starts with an equals sign =. That equals sign is the signal to Excel that what follows is a calculation, not text. Without it, Excel treats whatever you type as plain text and stores it as-is.

After the equals sign, you can write arithmetic directly, reference cells, or call a function — or combine all three. Here is the anatomy of a formula:

Functions are pre-built formulas that Excel provides. Instead of writing a long addition like =B2+B3+B4+B5+B6+B7+B8, you call the SUM function with a range: =SUM(B2:B8). Same result, far less typing, and it handles any number of rows automatically.

Basic Arithmetic Operators

Before we get into functions, here are the arithmetic operators you can use directly in any formula. These work exactly like a calculator:

=B2+C2

=B2-C2

=B2*C2

=B2/C2

=B2^2

=A2&" "&B2

SUM — Add a Range of Numbers

SUM is the most commonly used function in Excel. It adds up every number in the range you give it. You can sum a column, a row, a block, or a mix of separate cells.

=SUM(B2:B8)           Sum a column range
=SUM(B2:F2)           Sum a row range
=SUM(B2:D8)           Sum a block of cells
=SUM(B2,D5,F8)        Sum specific non-adjacent cells
=SUM(B2:B8, D2:D8)    Sum two separate ranges together

=SUM(B2:B7)

AVERAGE — The Mean of a Range

AVERAGE calculates the arithmetic mean — it adds up all the values and divides by how many there are. It automatically ignores empty cells (but not cells containing zero).

=AVERAGE(B2:B7)

A useful companion is AVERAGEIF — the same as AVERAGE but only for rows matching a condition, like the average sales for a specific region. We will cover that in the Logical Functions lesson.

COUNT, COUNTA, COUNTBLANK

The COUNT family of functions tells you how many cells contain something. They are more useful than they first appear — especially when your data has gaps or you need to validate whether a column is fully filled in.

=COUNT(B2:B100)        How many numeric values in B2:B100
=COUNTA(A2:A100)       How many non-empty cells in A2:A100
=COUNTBLANK(A2:A100)   How many empty cells in A2:A100

A common pattern is to use =COUNTA(A:A)-1 to count the number of data rows in a column — subtracting 1 to exclude the header row. Clean and simple.

MIN and MAX — Smallest and Largest

MIN returns the smallest value in a range. MAX returns the largest. Both ignore empty cells and text.

=MIN(B2:B7)     Lowest monthly sales figure
=MAX(B2:B7)     Highest monthly sales figure

You can also combine them — for example, to calculate the range between the lowest and highest: =MAX(B2:B7)-MIN(B2:B7). Useful for spotting how spread out your data is.

ROUND, ROUNDUP, ROUNDDOWN

Numbers from calculations often come with long decimal tails. The ROUND family lets you control how many decimal places your result shows — and unlike simply formatting a cell to show fewer decimals, ROUND actually changes the stored value.

=ROUND(number, num_digits)

=ROUND(17100.666, 2)      →  17100.67   (rounds to 2 decimal places)
=ROUND(17100.666, 0)      →  17101      (rounds to nearest whole number)
=ROUND(17100.666, -2)     →  17100      (rounds to nearest hundred)

=ROUNDUP(17100.1, 0)      →  17101      (always rounds up, even if .1)
=ROUNDDOWN(17100.9, 0)    →  17100      (always rounds down, even if .9)

Use ROUND when accuracy matters — for example, in financial reports where displaying 17,100.67 as 17,101 due to formatting could create a discrepancy between what is shown and what is calculated.

Putting It All Together — A Sales Summary

Here is a practical example of all these functions working together on a real business dataset. This kind of summary block is something you will build in almost every reporting project:

Formula Errors — What They Mean

When a formula cannot calculate correctly, Excel shows an error code instead of a result. These are not random — each error code tells you exactly what went wrong. Knowing what each one means saves a lot of debugging time:

Next up — Text Functions, where you will learn how to clean, extract, combine, and transform text data using functions like LEFT, RIGHT, MID, TRIM, UPPER, and more.