Square Feet:
Abbreviations: SqFt, Sq.Ft., sq.ft., ft2, Ext. SqFt
A.K.A. (also known as): Ext. SqFt = Exterior Square Feet
Exterior Square Feet (Ext. SqFt) is a term that we use to denote the total amount of siding material needed for a particular siding job including material waste.

Square Feet are just more than one Square Foot.  (i.e. - 1 square foot, 2 square feet)

So what is a "square foot"? 

A "square foot" is a unit of area measurement equal to a square measuring one foot on each side,  see example below; 0.0929 square meters. Abbrev.: ft2, sq. ft.

Using the formula above, let's bring this all together.

Example:  You have a wall on your house that is 10 feet tall by 10 feet wide. ( 10' x 10' )

What is the square footage of this wall?

Answer: 10' x 10' = 100 ft2 (100 ft2 = 100 SqFt = 100 sq.ft. = 100 Ext. SqFt)

Now if a product costs $1.50 psf (per square foot) and you need 100 sq.ft. your cost would be $150.00.

$1.50 psf  x  100 sq.ft.  =  $150.00

How-To Calculate Your Exterior Square Feet