How Do You Calculate Square Feet?

Readers Digest, March 2013, submitted by Terri Hanke, Kansas:

The front office asked us to figure out the square footage dedicated to each department in our clothing store. To save time, I suggested we count the ceiling tiles above each department.

"They're each two square feet. Counting the tiles would give us an accurate dimension of each department without having to work around all the displays," I explained.

My boss hated the idea. "He-lloo," she said, sarcastically, "we need the square footage of the floor, not the ceiling."