How Does Excel Work?

If you've ever wondered what's actually happening when you type a number into a cell or watch a formula update automatically, this post breaks it down in plain English.

Contents:

1. Quick Answer

2. The Grid: Columns, Rows, and Cells

3. How Excel Stores Data

4. How Formulas Work

5. How Excel Knows When to Recalculate

Quick Answer

Excel is a spreadsheet application that organizes data into a grid of rows and columns, where each intersection (a "cell") can hold a value, text, or a formula that calculates a result automatically. When you change a value that a formula depends on, Excel recalculates the result instantly. Everything you see in a workbook is built on top of that single idea.

The Grid: Columns, Rows, and Cells

Excel's workspace is a grid. Columns run vertically and are labeled with letters (A, B, C... Z, AA, AB...). Rows run horizontally and are labeled with numbers (1, 2, 3...).

Every intersection of a column and a row is a cell, and every cell has an address, like B4 or J17. That address is how formulas reference data from other parts of the sheet.

If you want a deeper look at the layout, Understanding the Basic Layout of Excel walks through it in more detail.

How Excel Stores Data

Each cell can hold one of three things:

• A value (a number, a date, or text you've typed directly)

• A formula (an instruction to calculate something)

• Nothing at all (empty)

What you see in the cell and what the cell actually contains can be different. If you type = 10 * 5 into a cell, you'll see 50 on screen, but the cell contains the formula. You can always check by clicking a cell and looking at the formula bar at the top of the screen.

Dates are a good example of this separation. Excel stores every date as a serial number (January 1, 1900 = 1, January 1, 2024 = 45292, and so on). The date format you see is just a display setting layered on top of that number. This is why calculating the number of days between two dates is as simple as subtracting one date from another.

How Formulas Work

A formula is an instruction that starts with an equals sign. When Excel sees =, it knows not to treat what follows as plain text but to evaluate it as a calculation.

= A1 + A2

This formula tells Excel to take whatever value is in A1, add the value in A2, and display the result. The formula itself stays stored in the cell; only the result is shown.

Functions are pre-built formulas that handle more complex operations. SUM, AVERAGE, and IF are functions. You call them by name, pass in your data as arguments inside parentheses, and Excel does the calculation.

= SUM(A1:A10)

This adds up every value from A1 through A10. Excel ships with hundreds of built-in functions covering math, text, dates, logic, lookups, and more. If you're just getting started with them, Basic Excel Formulas and Functions is a good place to begin.

How Excel Knows When to Recalculate

Excel tracks which cells each formula depends on. This is called the dependency tree. When a cell that a formula references changes, Excel flags that formula for recalculation and updates the result immediately.

This happens automatically by default (Automatic Calculation mode). You can switch to Manual Calculation mode if you have a very large workbook and want to control when recalculation happens, but for most users, automatic is the right setting.

That chain reaction is what makes spreadsheets powerful. Change one input, and every formula that depends on it (directly or indirectly) updates across the entire workbook without you having to touch them.