If each side of a square is 5 units long, how many total units are there in the perimeter?

To find the perimeter of a square, you need to add together the lengths of all four sides. Since each side of the square is given as 5 units long, you can calculate the perimeter using the formula:

Perimeter = 4 × (length of one side).

In this case, with each side measuring 5 units, the calculation becomes:

Perimeter = 4 × 5 = 20 units.

Thus, the total perimeter of the square is 20 units, making it the correct choice. Understanding the formula for the perimeter of a square is essential, as it simplifies the calculation to a multiplication of the side length by four. This approach helps ensure accuracy when determining the perimeter of any square, regardless of the length of the sides.