Free tool
Load factor calculator
Convert between usable and rentable square feet, derive the load factor, and see what a quoted rate costs per usable foot.
Result
Load factor and add-on factor are sometimes quoted differently. Confirm which measure the lease uses, since BOMA standards define several.
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Load factor is a negotiating term, not a physical fact
Although load factor is derived from measured areas, which areas count as common is a matter of measurement standard and negotiation. BOMA publishes several standards, and they do not produce identical numbers for the same building.
That is why the lease should state the measurement standard and the rentable area as an agreed figure rather than leaving it to be recomputed. A rentable area that shifts between the letter of intent and the executed lease is a rent increase in disguise.
Questions
What is the difference between rentable and usable square feet?
Usable square footage is the space inside the demised premises, which is what the tenant actually occupies. Rentable square footage adds that tenant’s proportional share of building common areas such as lobbies, corridors, and restrooms. Rent is quoted and billed on the rentable figure.
How is load factor calculated?
Divide rentable square feet by usable square feet and subtract one. A 10,580 RSF suite with 9,200 usable square feet carries a load factor of about 15%. Some markets quote the same relationship as an add-on factor or a common area factor.
What is a typical load factor?
Multi-tenant office buildings commonly fall between 10% and 20%. Single-tenant buildings can approach zero because there is little shared common area to allocate. A load factor well above 20% is worth questioning, since it materially raises effective rent.
Why does load factor matter when comparing spaces?
Two suites quoted at the same rate per rentable square foot can cost meaningfully different amounts per usable square foot. Comparing on the effective rate per usable square foot, which this calculator produces, puts competing spaces on the same basis.
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