Width of a Rectangle Calculator

The width of a rectangle calculator can take two dimensions of your rectangle (height, area, diagonal, or perimeter) and work out the width of your rectangle. We'll also show you some formulas for the width of a rectangle, that are based on what information you have available. So don't be a square and read on!

Using the width of a rectangle calculator is easy, with only two steps. Here's how.

• Enter the dimensions that you know of the rectangle.
• Find your rectangle width in the bottom box.
• The calculator is omni-directional — if you want to work backwards instead, you can change the rectangle's width and see how its other dimensions react.
• And that's it! Now you know how to calculate the width of a rectangle!

Depending on what information you have available, there are many ways to calculate the width of a rectangle.

• If you have the area A and length h, its width w is w = A/h.
• If you have the perimeter P and length h, its width is w = P/2−h.
• If you have the diagonal d and length h, it's width can be found with w = √(d²−h²).
• If the rectangle's length is not known, you'd need to do some algebra with the quadratic equation to solve for the width.

That's a lot of different formulas for the width of a rectangle! It's because there are multiple equations that govern the dimensions of a rectangle. Here they are:

where:

• $w$ is the rectangle's width;
• $h$ is the rectangle's length;
• $A$ is the rectangle's area;
• $P$ is the rectangle's perimeter; and
• $d$ is the length of the rectangle's diagonal (as described by the Pythagorean theorem).

Here's a neat visual:

If the width of a rectangle calculator isn't quite what you want, try out our other rectangular calculators:

• Area of a rectangle calculator
• Dimensions of a rectangle calculator
• Diagonal of a rectangle calculator
• Rectangle diagonal angle calculator
• Perimeter of a rectangle
• Surface area of a rectangle calculator
• Length of a rectangle calculator
• Length and width of rectangle given area calculator
• Length and width of rectangle given perimeter calculator
• Perimeter of a rectangle with given area
• Rectangle scale factor calculator
• Square feet of a rectangle calculator
• Golden rectangle calculator

A rectangle has four sides, but because the sides are paired, there are only two unique dimensions. Conventionally, the width is the shortest of these two dimensions, but when the rectangle is presented as lying on its side, the horizontal side is usually called the width.

Using the formula for a rectangle's area, A = h × w, we can follow these steps:

1. Rewrite the area formula to make the width w the subject of the equation: w = A/h.
2. Plug in the values: w = 20/4.
3. Do the math and find that w = 5 m.