The purpose of the Standard Method For Measuring Floor Area in Office Buildings is to permit communication and computation on a clear and understandable basis. The BOMA Standard has been the generally accepted method for measuring office space for many years. It should be noted that this standard can and should be used in measuring office space in old as well as new buildings. It is applicable to any architectural design or type of construction.

Usable Area

This method measures the actual occupiable area of a floor or an office suite and is of prime interest to a tenant in evaluating the space offered by a landlord and in allocating the space required to house personnel and furniture. The amount of Usable Area on a multi-tenant floor can vary over the life of a building as corridors expand and contract and as floors are remodeled. Usable Area can be converted to Rentable Area by the use of a conversion factor. The Usable Area of an office shall be computed by measuring to the finished surface side of the office side of corridor and other permanent walls, to the center of the partitions that separate the office from adjoining Usable Areas, and to the inside finished surface of the dominant portions of the permanent outer building walls. No deduction shall be made for columns and projections necessary to the building.

The Usable Area of a floor shall be equal to the sum of all Usable Areas on that floor.

Rentable Area

This method measures the tenant's pro-rata portion of the entire office floor, excluding elements of the building that penetrate through the floor to areas below. The Rentable Area of a building is fixed for the life of a building and is not affected by changes in corridor sizes and configuration. This method is therefore recommended for measuring the total income producing area of a building and for use in computing the tenant's pro-rata share of a building for purposes of rent escalation. The Rentable Area of floor area shall be computed by measuring to the inside finished surface of the dominant portions of the permanent outer building walls, excluding any major vertical penetrations of the floor.

No deduction shall be made for columns and projections necessary to the building. The Rentable Area of an office on the floor shall be computed by multiplying the Usable Area of that office by the quotient of the division of the Rentable Area of the floor by the Usable Area of the floor resulting in the R/U Ratio.

Load Factor

The Load Factor is the percentage of space on a floor that is not usable, expressed as a percent of Usable Area. It is also known as the Common Area Factor or the Loss Factor.

Rentable Area ÷ Usable Area = R/U Ratio

Conversion Formulas

Definitions