HTML & CSS · The Box Model · Lesson 7 of 25

Understanding the Box Model

Concept

Understanding the Box Model

Every element is a box made of content, padding, border, and margin, counted from the inside out.

Padding adds space inside the border (and gets the element's background color), while margin adds space outside the border and is always transparent.

By the end of this lesson

Explain the core idea behind Understanding the Box Model.
Predict output before running a change.
Test one realistic and one unusual input.
Use the result to make the next decision.

How to study this page

1. Read one concept.
2. Change the example.
3. Run, compare, and explain.
4. Complete the challenge below.

Syntax

.selector {
  padding: 16px;
  border: 1px solid color;
  margin: 12px;
}

ExampleRunnable

.card {
  padding: 16px;
  border: 1px solid #ccc;
  margin: 12px;
}

Try it Yourself »

Different values per side

.card {
  padding: 10px 20px; /* top/bottom 10px, left/right 20px */
  margin: 8px 0 8px 0; /* top right bottom left */
}

Note: The four-value shorthand always goes clockwise: top, right, bottom, left.

Self-check before continuing

Without looking at the example, describe what changes when you modify one input in Understanding the Box Model. Then reopen the editor and prove your explanation with a small test.

You are ready to continue when you can predict, test, and explain the result.

Your turn

Create a box with 20px padding, a 2px border, and 10px margin.

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Console

Output will appear here...