Can someone tell me how to get the correct square footage of living space for a home? What measurements should I take to compile this number? And what areas do not come into consideration? Thanks. Dave.

Square foot is measured by multiplying the length by the width of a room, a building, the yard, etc. any flat space.

If say a rectangle single family home, one story, with a basement, attached garage, and one small finished room, say a den, in the basement. The livable areas are the first floor and the den in the basement.

Measure the den inside from wall to wall, 20 ft length and the width, 15 ft.
A=LW
A=20 x 15
A=300 sq ft.

For the firsrt floor, just measure the outside, side to side 60 ft and front to back, 25 ft.

A=LW
A=60 x 25
A=1500 sq ft.

Total sq ft of living space is 1500 + 300 = 1800 sq ft.

If the building is odd shaped, break it down into small rectangles, add the products of each, and all the products for the total.

Length times width of each floor. It doesn't include a basement unless it is finished to code (windows & doors with proper egress specs) A garage is not included and the attic in not included unless there are finished rooms.
Example: if you have a ranch/ single story house on a slab, no garage, say 40' long by 32' wide that equals 1280'. Your house is 1280sq ft.

You beat me to it TK

In some locations, basements are not included in sq footage calculations even if they are finished. Don't know the exact details, but I do know that the finished room in my basement does not count towards the total square footage of my house.

Here in Kentucky the basement is only included if it is a walkout basement(sometimes called a daylight basement).

Check With A Realator In Your Area To See If The Basement Is Included.

Ya-all have addressed a room that's a perfect square or rectangle . But what if this room has a built out bay or small addition?
You lay out the larger room as a perfect square or rectangle and multiply L X W and measure the smaller bay as a separate room and add the two together for a total footage. Cheer, Tom

Yom Tom, did you see when this was asked? We were young back then