Most boxes are 6 sided . . . 4 sides, a top and a bottom.
Joking aside, I assume you're asking about a hexagon, a geometric figure with 6 sides, all of equal length.
A hexagon is made up of 6 equilateral trianges, so calculate one triangle and multiply by 6.
The formula for the area of an equilateral triangle is: (square root of 3 divided by 4) * length of one side squared. Multiply the answer by 6 to get the area.
As an example, assume each side equals 8 inches.
(square root of 3 divided by 4) * length of one side squared
(1.73205 / 4) * 64 = 27.7128 square inches per triangle * 6 = 166.2768 total square inches.
166.2768 square inches / 144 = 1.1547 square feet