Finding the area of a square is very easy if you know the lengths of its sides, perimeter, or diagonals. Here's how to find it.
Step
Method 1 of 3: Using Side Length
Step 1. Write down the side lengths
Suppose a square has a side length of 3 cm. Write it down.
Step 2. Know the formula for finding the area of a square (Area=side^2)
Since all squares have the same side length, you just need to multiply the side length of the square by itself. If the side of a square is 3 cm, then you only need to square 3 cm to find the area of the square. 3cm x 3cm = 9cm^{2}.
Step 3. Don't forget to write the units in square form
You've finished it.

Squaring the sides of a square is the same as multiplying the height of the square by the base.
Method 2 of 3: Using a Known Diagonal Length
Step 1. Measure the length of the diagonal of the square
Step 2. Multiply the result of measuring the diagonal length of the square by itself
Square the length of the diagonal. Suppose a square has a diagonal of 5 cm. Now, square the length of the diagonal. 5cm x 5cm = 25cm^{2}.
Method 3 of 3: Using a Known Perimeter
Step 1. Multiply the perimeter by 1/4 to find the length of the side
This is the same as dividing the perimeter by 4. Since a square has four sides and each side is the same length, you can find the side length of a square simply by dividing the perimeter by 4. Let's say the perimeter of a square is 20 cm. Multiply 20 cm by 1/4: 20 cm x 1/4 = 5 cm. Thus, you know that the length of the side of the square is 5 cm.
Step 2. Multiply the length of the side of the square by itself
Square the side length. Since you already know that the side length is 5 cm, you can square it to find the area of the square. Area = (5 cm)^{2} = 25 cm.^{2}