Reviewed by Robert Mendieta Jr., CCIM — Associate Broker · Commercial Division · DRE #01422904
Last updated: October 3, 2026
Rentable vs usable square feet is the gap between the space you actually occupy and the number your rent is calculated on. In a multi-tenant office building, the lease quotes the larger figure: your suite plus a share of the lobbies, corridors and restrooms everyone uses. The ratio between them is the load factor.
The direct answerWhat’s the Difference Between Rentable vs. Usable Square Feet?
Usable square feet is the area inside your suite that only you occupy. Rentable square feet is that usable area plus your allocated share of the building’s common areas, applied through a load factor. Commercial rent is quoted on rentable square feet, so you pay for more area than you can put furniture in.
| Usable square feet (USF) | Rentable square feet (RSF) | |
|---|---|---|
| Measures | The area within your own suite | Your suite plus a share of service and amenity areas |
| BOMA term | Occupant area (2010 office standard) | Rentable area |
| Used for | Cleaning costs and space efficiency | Quoting rent and benchmarking |
Per BOMA International
BOMA published its first office measurement standard in 1915. The current edition, ANSI/BOMA Z65.1-2024, exists primarily to calculate Rentable Area.
Key Takeaways
- Usable is your suite; rentable adds a share of common areas, and rent is quoted on rentable.
- Hypothetically, 2,000 usable feet at a 15% load factor is 2,300 rentable feet.
- BOMA’s 2010 office standard: Method A sets a load factor per floor; Method B, one per building.
- A lower quoted rate can cost more. Compare on cost per usable square foot.
- Plan and field measurements commonly differ; ask for a remeasurement right.
What Are Usable Square Feet?
Usable square feet are the floor area inside your own suite, the space only your business occupies. BOMA’s 2010 office standard calls it occupant area, and BOMA notes it is often used to determine cleaning costs and space efficiency.
The billed areaWhat Is Rentable Square Footage — and What Common Areas Get Added?
Rentable square footage is your usable area plus an allocated share of the building’s shared service and amenity areas, applied by a load factor. Think lobbies, corridors and restrooms, allocated among the tenants who share them.
BOMA’s office standards exclude parking from common area and rentable area, and BOMA’s 2010 office standard defines a major vertical penetration, such as a shaft, as a floor opening over 1 square foot. Some landlords quote a “market” load factor instead of a measured one.
The mathHow Do You Calculate the Load Factor in Commercial Real Estate?
Divide rentable by usable square feet to get the R/U ratio; subtract 1 to state it as a percentage. A 1.15 ratio and a 15% load factor mean the same thing: 1,000 usable square feet pays rent on 1,150.
Hypothetical example
2,000 usable square feet × 1.15 = 2,300 rentable square feet; 300 of them are common-area share. Working backward, 5,000 rentable square feet ÷ 1.18 is about 4,237 usable square feet.
The percentage is also called the common area factor or add-on factor. A loss factor, (rentable − usable) ÷ rentable, looks smaller: the hypothetical 15% load factor above is a 13.0% loss factor. Our commercial real estate glossary defines it the same way. For how this factor affects your improvement allowance, see our guide to tenant improvement allowance.
Building designWhy Do Load Factors Differ From Building to Building?
Layout and measurement method drive it. Under BOMA’s 2010 office standard, Method A gives each floor its own load factor and Method B applies one to the entire building; the owner picks one and uses it building-wide. Under Method A, floors with a single whole-floor tenant typically see smaller load factors.
Market vs. measured · BOMA 2010 office standard
A “market” load factor cannot raise the factor calculated on BOMA’s Global Summary of Areas. When a market factor is used, the lesser of the two is the capped load factor.
A lease can still state whatever factor the parties agree to. Before comparing listings on our Inland Empire office market page, convert each quote.
Apples to applesHow Do You Compare Two Spaces With Different Load Factors?
Convert every quote to cost per usable square foot. Identical usable area can carry different rents when load factors differ.
| Hypothetical | Suite A | Suite B |
|---|---|---|
| Usable SF × R/U ratio | 2,000 × 1.12 | 2,000 × 1.20 |
| Rentable SF | 2,240 | 2,400 |
| Quoted rate (per RSF, monthly) | $2.00 | $1.90 |
| Monthly rent | $4,480 | $4,560 |
| Cost per usable SF | $2.24 | $2.28 |
Suite B’s lower rate costs $80 more a month, $960 a year. Lease structure matters too: a triple net (NNN) lease and a full-service gross quote cover different expenses; see the types of commercial leases and our gross vs. net lease breakdown.
Before you signCan You Negotiate the Load Factor or Challenge the Measurement?
Yes. Rentable area and load factor are lease terms; BOMA makes no recommendation on how leases are written. Plan-based area commonly differs from field measurements, and BOMA calls for documented, verifiable calculations. Ask which standard, edition and method was used, and whether the figure is measured or a market factor. For how to state these figures up front, see our guide to the commercial lease letter of intent.
Hypothetical remeasurement
A lease states 2,300 rentable square feet; remeasurement finds 2,250. At $2.00 per rentable foot monthly, that is $100 a month, $1,200 a year and $6,000 over a 5-year term.
A GSA lease clause, 48 CFR 552.270-20, models a fix: if less usable (ABOA) space is delivered than agreed, annual rent is cut by the missing feet times one plus the common area factor, times the rate per rentable square foot. It applies only to GSA leases that include it, not to private leases. Tenant representation requests the measurement report early; see leasing commercial property step by step. For how this plays out at your next option period, see our guide to commercial lease renewal.
Not legal advice. Apex is not a law, tax or accounting firm. Have your attorney review any measurement or remeasurement language before you sign.
Does the Load Factor Apply to Retail and Industrial Space?
Not in the same way. BOMA’s retail standard, ANSI/BOMA Z65.5-2025, centers on Gross Leasable Area. BOMA’s published interpretations add that common areas are not loaded into GLA; their costs are normally shared by GLA instead. That shows up in your CAM charges and pro-rata share. BOMA’s industrial standard, ANSI/BOMA Z65.2-2025, does calculate rentable area and can generate multiple load factors for shared space types. Single-occupant office buildings often lease on gross area instead, by the parties’ choice. At year-end, your pro-rata share of actual costs is trued up; see our guide to CAM reconciliation.
Common questionsRentable vs. Usable Square Feet: Frequently Asked Questions
Do you pay rent on rentable or usable square feet?
In multi-tenant office leasing, you pay on rentable square feet: your usable area plus your share of the building’s common areas.
What is a good load factor for office space?
There is no single number; it depends on the building, floor and measurement method. Under Method A of BOMA’s 2010 office standard, floors with a single whole-floor tenant typically see smaller load factors. We know of no published Inland Empire range, so compare quotes on cost per usable square foot.
How do I convert rentable square feet to usable square feet?
Divide rentable square feet by the R/U ratio. Hypothetically, 5,000 rentable square feet at a 1.18 ratio is about 4,237 usable square feet.
What is BOMA and why does it matter in a lease?
BOMA International has set building measurement standards since 1915 and is the ANSI secretariat for them. Its standards define how space is measured, not how leases are written, so your lease should name the standard and edition.
Is the load factor negotiable?
Yes. The lease governs, so negotiate before signing. Some landlords use a market load factor, which under BOMA’s 2010 office method can cap, but not raise, the measured factor. Ask for a remeasurement right, reviewed by your attorney.
Does the load factor apply to warehouses and retail space?
Retail does not load common areas into Gross Leasable Area under BOMA’s retail standard. BOMA’s industrial standard does calculate rentable area, with multiple load factors for shared space types.
Measure it before you sign it
Robert Mendieta Jr., CCIM — Associate Broker · Commercial Division, DRE #01422904 — brings more than 20 years of commercial real estate experience to converting quotes and negotiating measurement terms.
Call Robert: (951) 977-3251Or request a free CRE consult with the form below.
Sources
- BOMA International · BOMA Standards · September 23, 2026
- BOMA International · Floor Standards Interpretations: Best Practice Guidance · September 23, 2026
- eCFR · 48 CFR 552.270-20, Payment · current as of September 1, 2026
Robert Mendieta Jr., CCIM · Associate Broker · Commercial Division · DRE #01422904 · Apex Real Estate Services · 3750 E. Florida Ave Suite A, Hemet, CA 92544 · (951) 977-3251