Rectangle Side Calculator: Find the Unknown Side of a Rectangle

In geometry, a side can be defined as a line connecting two vertices of a figure or two-dimensional figure. Our online calculator will help you find the side, edge of more than 11 shapes.

Rectangle — is a quadrangle in which all angles are straight (equal to 90 degrees). In Euclidean geometry, for a quadrilateral to be a rectangle, it is enough that at least three of its angles are straight, then the fourth angle, by the theorem on the sum of the angles of a polygon, will also be 90 °.

If you need to find the length of one of the sides of a rectangle, our free online rectangle side calculator can help. The rectangle side can be found by the diagonal and other side, according to the Pythagorean theorem, since the diagonal divides the rectangle into two equal right triangles. Simply input the known side and dioganals lengths of the rectangle, and our calculator will find the length of the unknown side.

Rectangle Side Formula

The formula to calculate the length of a side of a rectangle is:

b = \sqrt{d^2 - a^2}

where d is the dioganal of the rectangle, b is the length of the rectangle, and a is the width of the rectangle.

Using the formula above, you can rearrange it to solve for any of the sides.

Example Problems

Here are some examples of how to use the formula to find the length of a side of a rectangle.

Example 1

Find the length of a rectangle with a width of 5 units and an dioganal of 15 units.

We can use the rectangle side formula to solve for the length of the rectangle:

b = \sqrt{15^2 - 5^2}

b = 14.14

Therefore, the length of the rectangle is 14.14 units.

Example 2

Find the width of a rectangle with a length of 10 units and an dioganal of 35 units.

We can use the rectangle side formula to solve for the width of the rectangle:

b = \sqrt{35^2 - 10^2}

b=33.54

Therefore, the width of the rectangle is 33.54 units.

Use our free online calculator to find the length of the unknown side of a rectangle. Simply enter the known length/width and dioganal of the rectangle, and our calculator will use the rectangle side formula to find the length of the unknown side.

Using our calculator can save you time and prevent calculation errors. Try it out today!