Area of a Rectangle Notes

Published on: September 29, 2026

This Area of a Rectangle Calculator finds the space inside a rectangle from its width and its length, and shows the working line by line. A rectangle is covered by rows of unit squares, with one row for every unit of width, so multiplying the width by the length counts every square inside it. The answer is written in square units. Following the same pattern every time is what makes the area of a rectangle easy to picture, check, and work out on your own.

Rectangle with sides labeled w and l

In the diagram, the width is \(w\) and the length is \(l\).

Step-by-step method

  1. Set up the problem.
  2. Write the formula.
  3. Substitute the width and the length into the formula.
  4. Work out the area.

Formula:

\(A = wl\)
See Example 1 Hide Example 1

Problem

\(w = 8, l = 6\)

Approach

Step-by-step method

  1. Set up the problem.
  2. Write the formula.
  3. Substitute the width and the length into the formula.
  4. Work out the area.

Step 1

Step 1 - Set up the problem.

In this problem: We are finding the area of a rectangle whose width is \(w = 8\) and whose length is \(l = 6\).

\(w = 8,\; l = 6\)

Step 2

Step 2 - Write the formula.

In this problem: A rectangle is covered by rows of unit squares, with one row for every unit of width, so its area is the width multiplied by the length.

\(A = wl\)

Step 3

Step 3 - Substitute the width and the length into the formula.

In this problem: Replacing \(w\) with \(8\) and \(l\) with \(6\) in \(A = wl\) gives \(A = 8 \times 6\).

\(A = 8 \times 6\)

Step 4

Step 4 - Work out the area.

In this problem: Multiplying the width by the length gives \(8 \times 6 = 48\).

\(A = 8 \times 6 = 48\)

Final Answer

\(A = 48\)
See Example 2 Hide Example 2

Problem

\(w = 2.5, l = 3\)

Approach

Step-by-step method

  1. Set up the problem.
  2. Write the formula.
  3. Substitute the width and the length into the formula.
  4. Work out the area.

Step 1

Step 1 - Set up the problem.

In this problem: We are finding the area of a rectangle whose width is \(w = 2.5\) and whose length is \(l = 3\).

\(w = 2.5,\; l = 3\)

Step 2

Step 2 - Write the formula.

In this problem: A rectangle is covered by rows of unit squares, with one row for every unit of width, so its area is the width multiplied by the length.

\(A = wl\)

Step 3

Step 3 - Substitute the width and the length into the formula.

In this problem: Replacing \(w\) with \(2.5\) and \(l\) with \(3\) in \(A = wl\) gives \(A = 2.5 \times 3\).

\(A = 2.5 \times 3\)

Step 4

Step 4 - Work out the area.

In this problem: Multiplying the width by the length gives \(2.5 \times 3 = 7.5\).

\(A = 2.5 \times 3 = 7.5\)

Final Answer

\(A = 7.5\)
See Example 3 Hide Example 3

Problem

\(w = 9, l = 4\)

Approach

Step-by-step method

  1. Set up the problem.
  2. Write the formula.
  3. Substitute the width and the length into the formula.
  4. Work out the area.

Step 1

Step 1 - Set up the problem.

In this problem: We are finding the area of a rectangle whose width is \(w = 9\) and whose length is \(l = 4\).

\(w = 9,\; l = 4\)

Step 2

Step 2 - Write the formula.

In this problem: A rectangle is covered by rows of unit squares, with one row for every unit of width, so its area is the width multiplied by the length.

\(A = wl\)

Step 3

Step 3 - Substitute the width and the length into the formula.

In this problem: Replacing \(w\) with \(9\) and \(l\) with \(4\) in \(A = wl\) gives \(A = 9 \times 4\).

\(A = 9 \times 4\)

Step 4

Step 4 - Work out the area.

In this problem: Multiplying the width by the length gives \(9 \times 4 = 36\).

\(A = 9 \times 4 = 36\)

Final Answer

\(A = 36\)
See Example 4 Hide Example 4

Problem

\(w = 3.5, l = 2\)

Approach

Step-by-step method

  1. Set up the problem.
  2. Write the formula.
  3. Substitute the width and the length into the formula.
  4. Work out the area.

Step 1

Step 1 - Set up the problem.

In this problem: We are finding the area of a rectangle whose width is \(w = 3.5\) and whose length is \(l = 2\).

\(w = 3.5,\; l = 2\)

Step 2

Step 2 - Write the formula.

In this problem: A rectangle is covered by rows of unit squares, with one row for every unit of width, so its area is the width multiplied by the length.

\(A = wl\)

Step 3

Step 3 - Substitute the width and the length into the formula.

In this problem: Replacing \(w\) with \(3.5\) and \(l\) with \(2\) in \(A = wl\) gives \(A = 3.5 \times 2\).

\(A = 3.5 \times 2\)

Step 4

Step 4 - Work out the area.

In this problem: Multiplying the width by the length gives \(3.5 \times 2 = 7\).

\(A = 3.5 \times 2 = 7\)

Final Answer

\(A = 7\)