There are 4 ways to measure your building

Ask someone who might know– Sometimes a building has someone in charge of maintenance projects or a maintenance person; they usually will have plans to the building.  Subtract the tile from the total square feet of the office space– If your company leases the space you have, sometimes accounting will have the total square feet of the space you occupy. If you have the total square feet of the space, then all you have to do is subtract the all the tile from the total to get the carpet. Remember to include the restrooms in the total square feet of tile, or you will not subtract enough from the carpet. Count ceiling tiles–Ceiling tiles act kind of like a tape measure on the ceiling. This only works if you have a suspended ceiling. Most suspended ceiling tiles measure two feet by four feet. Then it is just a matter of counting the width by the length and multiplying to get the square foot of each room. Repeat this in every room, remember to write down whether the room is tile or carpet, and total each category.  Any combination of the above three or use a measuring wheel– They can be purchased at any local hardware store.