You would think that the topic of measuring the square footage of an apartment would be without controversy. After all, measuring tapes don’t lie, so what’s all the fuss about? Well, like almost any other aspect of NYC real estate, this one has some quirks that can cause confusion.

When buildings are first built, or converted, the sponsor is required to complete a “Schedule A” disclosing, among other things, the square footage of each residential unit being offered for sale. This Schedule A measurement is then used in the resale process, with brokers and homeowners relying on the original offering documents when advertising to the public the size of the apartment. But when buyers actually take the time to measure, or when they review appraisal reports prepared using internal unit measurements, they are often surprised to learn that the number is different – and smaller – than that advertised. Did the apartment shrink?

Most people if asked to measure an apartment would go room to room and take internal measurements of the livable space and then calculate the total. If the master bedroom is a square of 20 feet on each side, then the room would be 400 sq. ft. That makes sense. But it’s not how sponsors measure apartments. Here is the typical methodology: “each apartment is measure from the exterior face of the exterior walls to the midpoint of the interior walls and the midpoint of partitions separating one apartment from another.” Mechanical pipes, structural columns, shafts and conduits are included in this calculation even though, clearly, not usable space. Many exterior walls, especially in older buildings, can be as much as 24 inches thick. So the square room measured above if in the corner of such a building would now measure 22 feet by 22 feet, and the 400 sq. ft. room would now measure 484 sq. ft., an increase of 21%!

It’s important to remember to ask the right questions when talking square footage. What methodology was used in the calculation. As long as there is consistency in approach, relative measurements of one apartment to the next can be meaningful. But be sure to understand what is meant when a square footage is quoted, otherwise that beautiful new apartment might shrink.