Office Space Cost Calculator
Calculate the monthly rent, annual cost, and cost per employee for an office space. Enter the square footage, annual rent rate per square foot, operating expense rate, and number of employees. The calculator returns your base rent, total occupancy cost including operating expenses, and a per-employee cost to benchmark against budget targets.
Office space cost formulas
Annual base rent = sq ft * annual rate per sq ft
Monthly base rent = annual base rent / 12
Annual opex = sq ft * opex rate per sq ft
Annual total occupancy cost = annual base rent + annual opex
Cost per employee = annual total occupancy cost / employees
Sq ft per employee = total sq ft / employees
These formulas follow BOMA International standard measurement and occupancy cost conventions used in commercial real estate leasing.
Understanding office occupancy costs
- BOMA International defines usable area, rentable area, and common area factor; make sure quoted rates use the same measurement standard.
- Operating expenses in a NNN lease include property taxes, building insurance, and common area maintenance, paid proportionally by each tenant.
- Tenant improvement allowances reduce your effective cost; amortize any buildout costs you fund yourself over the lease term.
- GSA federal space standards provide a useful benchmark: 150 sq ft per person for traditional offices, 130 sq ft for open plan.
- Always request a full-floor plan with the lease to verify usable vs. rentable area before signing.
Office space costs: frequently asked questions
How is office space cost calculated?
Office space cost is typically quoted as an annual price per square foot. Monthly rent = (annual rate per sq ft * total sq ft) / 12. Total occupancy cost adds operating expenses (NNN costs such as taxes, insurance, and maintenance) to the base rent.
What is the difference between gross and NNN (triple net) leases?
A gross lease includes operating expenses in the quoted rent. A triple net (NNN) lease charges base rent plus the tenant's proportionate share of property taxes, building insurance, and common area maintenance (CAM). NNN leases have a lower quoted base rent but higher true cost.
How much space does each employee need?
BOMA International and GSA federal workplace standards suggest 150 to 250 square feet per person for traditional offices. Open-plan layouts typically use 75 to 150 sq ft per person. Remote-hybrid offices can operate at 50 to 100 sq ft per desk when utilizing hotdesking.
What other costs should I include in my office budget?
Beyond rent, budget for utilities (electricity, water, internet), janitorial services, security, tenant improvements (buildout), signage, parking, and renter's insurance. These can add 20% to 40% to base rent costs.
How do I compare office spaces with different lease structures?
Convert all options to a total annual cost per square foot including all operating expenses and tenant improvement amortization. This effective rate allows apples-to-apples comparison regardless of whether the lease is gross, modified gross, or NNN.
Official sources
- U.S. General Services Administration, Federal Workplace Standards: Workspace Strategy.
- BOMA International, Office Building Standards: BOMA Measurement Standards.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.