Surface Area Of A Cuboid Calculator Enter Length: Enter Width: Enter Height: Calculate A surface area calculator for a cuboid calculates the total surface area of a three-dimensional shape with six rectangular faces. The formula to calculate the surface area of a cuboid is: Surface Area=2LW+2LH+2wH Where: L is the length of the cuboid. W is the width of the cuboid. H is the height of the cuboid.