How to calculate the monthly rent of a commercial lease

Updated April 17, 2017

Commercial leases can set up base rental schedules in several different ways. Whether you have a monthly or yearly lease rate listed in your lease document, you can easily calculate the full amount of your monthly rent if you also know the amount of your property's operating expenses and your space's rentable square footage.

If your lease rate is spelt out in the lease document on yearly basis, identify the lease rate for the particular year and divide the amount by 12 to calculate your monthly base rental rate per square foot.

If your operating expenses are charged on yearly basis, identify the operating costs for the particular year and divide the amount by 12 to calculate your monthly operating expense rate per square foot. Operating expenses are often referred to as triple-net, or NNN rates.

Add together the monthly base rental rate and the monthly operating expense rate.

Multiply the amount by your rentable square footage. The will be your monthly rental cost.


Your lease document will not list the operating expense rate because the expense rate will change from year to year depending on taxes, energy costs and changes in service costs. Contact your property manager if you are unsure of your operating expense rate.

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About the Author

Jonathan Morgan began writing for Demand Media Studios in 2011. He contributes his expertise in business, personal finance and taxation to several online publications. Morgan holds a Bachelor of Science in economics from the United States Military Academy and is pursuing a Master of Taxation from Nova Southeastern University.