Rentable Square Footage (RSF) Calculator
Calculate the total billable area for a commercial lease. This tool determines your Rentable Square Footage (RSF) based on your private, Usable Square Footage (USF) and the building's common area Load Factor.
Enter your space's dimensions (Length and Width) and the building's Load Factor (%) provided by the landlord. The calculator finds the Usable Area and then applies the load to determine the final RSF.
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Understanding Rentable Square Footage & Formulas
What is Usable vs. Rentable Square Footage?
In commercial real estate, the area you pay for is different from the private space you occupy.
- Usable Square Footage (USF): This is the actual, private space that is exclusively for your use—the area inside the walls of your suite. It's calculated simply as Length × Width.
- Rentable Square Footage (RSF): This is the USF plus your proportional share of the building's common areas. These include lobbies, shared hallways, public restrooms, elevator shafts, and amenity centers. Landlords charge for these shared spaces via a "Load Factor."
The Rentable Square Footage (RSF) Formula
The calculation is straightforward once you have the Usable Square Footage and the Load Factor:
RSF = USF × (1 + (Load Factor / 100))
For example, if your USF is 1,000 sq ft and the Load Factor is 15%, your RSF is 1,000 × (1 + 0.15) = 1,150 sq ft. You pay rent on 1,150 sq ft.
What are BOMA Standards?
The Building Owners and Managers Association (BOMA) provides internationally recognized standards for measuring commercial spaces. These standards define precisely how to calculate Usable and Rentable areas, ensuring consistency and fairness across the industry. Most modern commercial leases adhere to BOMA measurement standards.
10 Calculation Examples
Click on an example to see the step-by-step calculation.
Example 1: Standard Small Office
Scenario: A small startup office suite.
1. Given Values: Length = 25 ft, Width = 20 ft, Load Factor = 15%.
2. Calculate USF: 25 ft × 20 ft = 500 sq ft.
3. Formula (RSF): RSF = USF × (1 + Load Factor %)
4. Calculation: RSF = 500 × (1 + (15 / 100)) = 500 × 1.15
5. Result: RSF = 575 sq ft.
Example 2: Metric-Sized Office
Scenario: An office measured in meters in a building with a high load factor.
1. Given Values: Length = 10 m, Width = 8 m, Load Factor = 20%.
2. Calculate USF (in sq m): 10 m × 8 m = 80 sq m.
3. Convert USF to sq ft: 80 sq m × 10.7639 = 861.11 sq ft.
4. Calculation (RSF): RSF = 861.11 × (1 + (20 / 100)) = 861.11 × 1.20
5. Result: RSF = 1,033.33 sq ft.
Example 3: Large Open-Plan Floor
Scenario: A large company leases a full floor with an efficient, low load factor.
1. Given Values: Length = 100 ft, Width = 80 ft, Load Factor = 8%.
2. Calculate USF: 100 ft × 80 ft = 8,000 sq ft.
3. Calculation (RSF): RSF = 8,000 × (1 + (8 / 100)) = 8,000 × 1.08
5. Result: RSF = 8,640 sq ft.
Example 4: Irregularly Shaped Space
Scenario: Your space is L-shaped, and you've already calculated the total Usable Area to be 1,250 sq ft.
1. Trick to use the calculator: Input the total area as the "Length".
2. Given Values: Length = 1,250 ft, Width = 1 ft, Load Factor = 12.5%.
3. Calculate USF: 1,250 ft × 1 ft = 1,250 sq ft.
4. Calculation (RSF): RSF = 1,250 × (1 + (12.5 / 100)) = 1,250 × 1.125
5. Result: RSF = 1,406.25 sq ft.
Example 5: Standalone Retail (No Load)
Scenario: A standalone retail building with its own entrance and no shared interior common areas.
1. Given Values: Length = 50 ft, Width = 30 ft, Load Factor = 0%.
2. Calculate USF: 50 ft × 30 ft = 1,500 sq ft.
3. Calculation (RSF): RSF = 1,500 × (1 + (0 / 100)) = 1,500 × 1
4. Result: RSF = 1,500 sq ft (In this case, RSF equals USF).
Example 6: Medium Office, Average Load
Scenario: A typical mid-sized office on a multi-tenant floor.
1. Given Values: Length = 50 ft, Width = 40 ft, Load Factor = 18%.
2. Calculate USF: 50 ft × 40 ft = 2,000 sq ft.
3. Calculation (RSF): RSF = 2,000 × (1 + 0.18) = 2,000 × 1.18
4. Result: RSF = 2,360 sq ft.
Example 7: Small Executive Suite
Scenario: A single executive office in a Class A building.
1. Given Values: Length = 15 ft, Width = 12 ft, Load Factor = 16%.
2. Calculate USF: 15 ft × 12 ft = 180 sq ft.
3. Calculation (RSF): RSF = 180 × (1 + 0.16) = 180 × 1.16
4. Result: RSF = 208.8 sq ft.
Example 8: Long, Narrow Gallery Space
Scenario: An art gallery with a narrow layout.
1. Given Values: Length = 80 ft, Width = 15 ft, Load Factor = 10%.
2. Calculate USF: 80 ft × 15 ft = 1,200 sq ft.
3. Calculation (RSF): RSF = 1,200 × (1 + 0.10) = 1,200 × 1.10
4. Result: RSF = 1,320 sq ft.
Example 9: Metric Warehouse Bay
Scenario: A bay in a large industrial warehouse, measured in meters.
1. Given Values: Length = 20 m, Width = 15 m, Load Factor = 5% (common for industrial).
2. Calculate USF (sq m): 20 m × 15 m = 300 sq m.
3. Convert USF to sq ft: 300 × 10.7639 = 3,229.17 sq ft.
4. Calculation (RSF): RSF = 3,229.17 × (1 + 0.05) = 3,229.17 × 1.05
5. Result: RSF = 3,390.63 sq ft.
Example 10: High-Amenity Building
Scenario: An office in a modern building with a large gym, lobby, and conference center, resulting in a high load factor.
1. Given Values: Length = 60 ft, Width = 50 ft, Load Factor = 25%.
2. Calculate USF: 60 ft × 50 ft = 3,000 sq ft.
3. Calculation (RSF): RSF = 3,000 × (1 + 0.25) = 3,000 × 1.25
4. Result: RSF = 3,750 sq ft.
Frequently Asked Questions (FAQs)
1. What is the difference between Usable and Rentable Square Footage?
Usable Square Footage (USF) is the private space you exclusively use. Rentable Square Footage (RSF) is the USF plus your share of the building's common areas. You pay your rent based on the RSF.
2. Where do I get the Load Factor number from?
The landlord, property manager, or their real estate broker must provide you with the Load Factor. It is a critical component of any commercial lease proposal and is typically non-negotiable for a specific building.
3. Is a higher Load Factor better or worse for me?
For a tenant, a lower Load Factor is financially better. It means a smaller percentage of your rent is going towards shared spaces, and more of it is for your own private, usable area.
4. My space is not a perfect rectangle. How do I use the calculator?
First, calculate your total Usable Square Footage manually (e.g., break the space into smaller rectangles and add their areas). Then, to use this tool, enter your total calculated USF into the "Length" field and enter "1" into the "Width" field. This allows you to directly input your USF.
5. What is a typical Load Factor percentage?
It varies greatly. For a full-floor tenant, it might be 5-10%. For a multi-tenant floor in a standard office building, it's often 12-20%. In a modern building with extensive amenities (large lobbies, gyms, etc.), it can exceed 20%.
6. Does this calculator work for metric measurements?
Yes. Select "Meters" from the unit dropdown. The tool will calculate the area in square meters, convert it to square feet (as RSF is a standard based on sq ft in North America), and then apply the load factor.
7. Why is my Rentable Square Footage always higher than my Usable?
Because the RSF includes your proportional share of the costs to build, operate, and maintain the building's common areas, which all tenants benefit from. The only time they would be equal is if the Load Factor is 0%.
8. What are BOMA standards?
BOMA (Building Owners and Managers Association) provides the official, standardized methods for measuring commercial real estate. These standards ensure that all parties are using a consistent and fair system to determine Usable and Rentable areas.
9. Is the Load Factor negotiable?
The building's overall Load Factor is fixed by its architecture and BOMA measurements, so it's generally not negotiable. However, all other terms of a lease, like the rental rate per square foot, are negotiable and can be adjusted to offset a high load factor.
10. Can I use this for industrial or retail space?
Yes. While most common in office leases, the concept can apply to other property types. Industrial spaces often have a very low load factor (e.g., 5-8%), while retail spaces in an enclosed mall will have a load factor to cover hallways and food courts.
