Instructions

1

Find the perimeter or "P" of the base of the pyramid by adding all the sides together. This formula is recognized as P=s+s+s if the base is a triangle. If the base is a square, simplify this equation by taking one side and multiplying it by 4.
2

Determine the area or "A" of the base of the pyramid. If the base of the pyramid is a square, multiply the length times the width. This formula is recognized as A=lw. If the base is a triangle, you need to multiply the base times the height and divide by two, where the height is referred to as the distance between the highest point of the triangle to the base of the triangle on a perpendicular axis. This formula is recognized as A=1/2 bh.
3

Calculate the surface area of the pyramid by multiplying the perimeter of the base by the slant height of the pyramid then dividing by two. Take this number and add it to area of the base. This formula is recognized as Surface Area (SA)=A+1/2(Ps). For example, if the base area is 100, the perimeter is 40, and the slant height is 5, insert the numbers into the formula to find the surface area. 100 + 1/2 (40 x 5) = 200.