To find the perimeter of a square, you can use the formula:
\[ \text{Perimeter} = 4 \times \text{side length} \]
If the side length of the square is 4 feet, then the perimeter is:
\[ \text{Perimeter} = 4 \times 4 \text{ ft} = 16 \text{ ft} \]
So, the perimeter of the square is 16 feet.