Last updated: September 27, 2026
Are loss factor and load factor the same?
They can describe the same difference between usable and rentable area using different denominators. In the convention used below, loss percentage divides that difference by rentable area; the load-factor add-on divides it by usable area. The rentable-to-usable multiplier is a third expression. Always ask which formula a quotation uses.
Define the areas before calculating
Let R be the rentable area assigned under the agreed measurement method and U the corresponding usable area. The examples below assume R is greater than U and both areas are positive. They illustrate the arithmetic; they do not establish how a building's boundaries or shared spaces should be measured.
External gross area, retail gross leasable area and office rentable area are not universally interchangeable. Use the property type, standard edition and area schedule specified for the transaction. Our BOMA guide and commercial floor-area guide explain the distinctions.
One difference, three expressions
Assume an illustrative area schedule assigns 25,000 rentable sq ft and 20,000 usable sq ft . Their difference is 5,000 sq ft.
Formulas using the stated convention
Expression Formula Example
Loss percentage (R − U) ÷ R × 100% 5,000 ÷ 25,000 × 100% = 20% Load-factor add-on (R − U) ÷ U × 100% 5,000 ÷ 20,000 × 100% = 25% Rentable/usable multiplier R ÷ U 25,000 ÷ 20,000 = 1.25
A 20% loss and a 25% add-on therefore describe the same assumed areas here. Calling both “20%” would change the calculation. Ask whether a quoted load factor is the 1.25 multiplier or the 25% add-on.
What does core factor mean?
Core factor is used in leasing discussions for an allocation or adjustment associated with shared building space. The label alone does not identify its denominator or the measured spaces included. Ask the landlord or measurer for the formula and the underlying area schedule instead of assuming core, loss and load percentages are numerically identical.
A suite and rent example
For illustration, assume the same uniform 1.25 multiplier applies to a suite with 1,000 usable sq ft. Its rentable area is 1,000 × 1.25 = 1,250 sq ft . The difference is 250 sq ft: 20% of the suite's rentable area or 25% of its usable area.
If the quoted base rent is $30 per rentable sq ft per year, annual base rent is 1,250 × $30 = $37,500 , or $3,125 per month. A quote based on usable area would require a different calculation. Taxes, operating expenses and other charges are separate unless the lease says they are included.
The suite's 1,000 ÷ 20,000 = 5% share of the assumed building usable area is not a 5% load factor. Tenant share and area adjustment answer different questions. A real building may have floor-specific allocations or other rules; do not apply a uniform multiplier unless the measurement schedule supports it.
Compare lease quotations consistently
Identify the measured areas, standard, edition and allocation method.
Write each percentage with its denominator and distinguish it from a multiplier.
Confirm whether the rent rate is annual or monthly and applies to rentable or usable area.
Review operating-expense allocations separately from the base-rent calculation.
Compare total occupancy costs and the space's suitability, not a factor in isolation.
Once the figures are reviewed, present their definitions and assumptions alongside the property information in CREOP marketing materials .