How Do I Properly Measure Office Space?

Before you can determine how much office space your business will need, you first need to understand how office space is measured for general rental purposes:

Usable Area

The Usable Area is the actual area that can be occupied on a floor or an office. 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.

The Usable Area of an office is calculated 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 main portions of the permanent outer building walls.

Rentable Area

The Rentable Area is the tenant's gross square footage of the entire office floor, minus  the elevator core, flues, pipe shafts, vertical ducts, balconies, stairwell areas and other similar columns and projections. The Rentable Area of a floor is fixed for the entire life of the building.  It is not affected by changes in corridor sizes and configuration.

The Rentable Area of an office floor is calculated by multiplying the Usable Area of that office by the result of the division of the Floor Rentable Area of the floor by the Usable Area of the floor resulting in the Floor Rentable/Usable Ratio.

Building Common Area

The Building Common Area includes all the areas of a building that are used to provide services to building tenants. These are areas which are not included in the office area of any specific tenant. It also includes any other common areas and is added to the Floor Rentable Area to calculate the Rentable Area.

Gross Rentable Area

Rent is almost always paid based upon the Gross Rentable Area which includes the Floor Rentable Area plus the pro rata share of Building Common Area.

Building Rentable Area + Pro Rata Building Common Area = Rentable Area

Load Factor

The Load Factor, or Rentable /Useable Ratio, is the percentage of space on a floor that is not usable plus a pro-rata share of the Building Common Area, expressed as a percent of Usable Area. AKA Common Area Factor or the Loss Factor. A Typical range is 10% to 18%.

Gross Rentable Area ÷ Usable Area = R/U Ratio

Conversion Formulas

• Load Factor (Load) = R/U Ratio - 1
• Rentable Area = Usable Area x R/U Ratio  
• Rentable Area = Usable Area x (1 + Load)
• Usable Area = Rentable Area ÷ R/U Ratio    

Definitions

Finished Surface:    

A wall, ceiling, or floor surface, including glass, as prepared for tenant use. It excludes the thickness of any additional surface additions such as paneling, carpet or other similar surface addition.

Major Vertical Penetrations:    

Stairs, elevator shafts, flues, pipe shafts, vertical ducts, and similar (including enclosing walls) which serve more than one floor of a building. It does not include stairs, lifts, and other similar structures which serve only one tenant occupying office space on 2 or more floors.