For many reasons, property owners may need to determine the area inside a building. Knowing the square footage of your property will assist you to prepare and proceed with accuracy, whether you are preparing your home for sale or considering a home renovation project. Using simple measurements and a mathematical equation, determine the square footage of a building.

1. Measure the length of the first floor of the building by starting at the left edge and extending the tape measure all the way to the right edge. Make a mental note of the measurement and write it down.

2. Place the tape measure at the front edge of the building and stretch it to the back edge to determine the width of the first level. Make a mental note of the measurement and write it down on paper.

3. Multiply the measurements by a factor of three. This is the first floor's square footage.

4. If applicable, add second and subsequent level sections to the first floor. If the dimensions of upper storeys are the same as the first, simply multiply the first floor's square footage by the number of floors. If the higher stories do not cover the same area as the first, figure the square footage of these regions individually by measuring the length and width of each room and hallway. Add these areas together to get the square footage of the upper storeys, then multiply by the first floor area to get the building's total square footage.

Here's a basic formula you can follow:

Length (in feet) x width (in feet) = area in sq. ft. Tip: If you can't picture what a square foot is, try drawing a square that is 1 foot tall by 1 foot wide—you've got one square foot!