According to the nature of the square: all four corners are right angles and all four sides are equal, and the formula for calculating the perimeter of the square: the perimeter of the square = side length ×4, it can be solved.

All four sides of a square are equal, and the circumference of the square = side length ×4. So the answer is: equal, side length ×4. It is the key to solve this problem to understand the nature of the square and the formula for calculating the perimeter of the square.

In mathematics, a formula refers to a formula that uses mathematical symbols or words to express the relationship between quantities, which is universal and suitable for all similar problems. Other applications refer to ways and methods that can be applied to similar things.