ITSO adopted the Residential Measurement Standard (RMS) from the Real Estate Council of Alberta (RECA). RMS is a consistent way to measure residential floor area so square footage is comparable and is not padded with space people cannot live in.
ITSO recommends RMS. It is not mandatory. The square footage field in the MLS® System is still required. If RMS was used, the RMS source flag may be selected. Do not select RMS unless the standard was actually followed.
RMS area is the sum of above-grade levels only. If any part of a level is below the ground, the whole level is below grade (including walkout basements) and is left out of RMS even if it is finished. Builder and MPAC figures are often larger because they can include open voids, non-livable space, or an exterior-only measure.
For information on how to use RMS, view the RMS guide.