CommLeaseCalc estimates the occupancy cost of a commercial space from inputs a tenant normally has at the start of a search: square footage, a quoted base rent, the period of that quote, the lease structure, an estimate of operating expenses, any separate monthly costs, a yearly rent increase, and a term. The goal is to turn a per-square-foot quote into a usable budget with a visible breakdown. It is not to model a specific lease document or to replace a landlord's expense statements.
This page describes every formula so that you can reproduce each result with a pencil or a spreadsheet. If the calculator and this page ever disagree, please tell us.
Let B be the base rent you typed, E the operating expenses you typed, P equal to 12 when the period is "per month" and 1 when it is "per year", A the square footage, O your other monthly costs, g the yearly increase as a decimal, and n the term in years.
With 2,500 square feet, base rent $24.00 per square foot per year, expenses $7.50, no other costs, 3% yearly increase, and a 5-year term: all-in rate $31.50; annual cost $78,750; monthly cost $6,562.50, shown as $6,563; base rent over five years is $60,000 × (1 + 1.03 + 1.0609 + 1.092727 + 1.12550881) = about $318,548; expenses are $18,750 × 5 = $93,750; the term total is about $412,298.
For a monthly quote of $2.00 per square foot with no expenses on 1,800 square feet: B×P = $24.00; annual cost $43,200; monthly cost $3,600.
It does not model free-rent periods, tenant improvement allowances, percentage rent, security deposits, present value, income taxes, or any clause that caps or excludes expenses. It does not use or publish market rents. Terms such as NNN, gross, and modified gross are used in the plain-language sense described in our lease structure guide; your lease may use different wording.
The definitions of net and gross leases in our guide follow the Cornell Law School Legal Information Institute (net lease, triple net lease). On measurement, the Building Owners and Managers Association (BOMA) publishes floor measurement standards, including ANSI/BOMA Z65.1 for office buildings (editions from 2017 and 2024 are listed on its site, boma.org). We do not apply any specific standard in the calculator; whether a given building was measured under one is a question for the lease. Content is reviewed by Numerlyn LLC before it is published. We revisit this page whenever the calculator logic changes. See the editorial disclosure.
Each input maps to a question a tenant is asked in real life. Square footage and base rent come straight from the listing. The period selector exists because the monthly and yearly conventions both appear in listings and a wrong guess changes the result by a factor of 12. The lease type decides whether operating expenses are added. The "other monthly costs" field covers items that are usually outside the rent, such as separately metered utilities. The increase and term fields give a first look at a multi-year commitment without turning the tool into a full lease-schedule model.
The big monthly number is the year-1 monthly cost rounded to the nearest dollar. For example, $6,562.50 is displayed as $6,563. Rates per square foot are shown with two decimals so that $31.50 does not appear as $32. Totals are rounded once at the end rather than at each step, which keeps the displayed numbers consistent with a spreadsheet that rounds only for display.
Blank or non-numeric entries are treated as zero. If the square footage is zero or less, the page shows a note instead of a meaningful result. If you choose a gross lease and also enter an operating-expense amount, a note explains that the amount is ignored. These checks do not catch every mistake, for example a rent that is ten times too high, so read the all-in rate and ask whether it looks like what the listing said.