Commercial rent is usually quoted as net rent plus TMI, in dollars per square foot per year. This commercial lease calculator turns that quote into what you will actually pay each month and over the whole lease. Rules checked October 4, 2026.
How the numbers work
- Net rent is the rent for the space itself. Area × rate per square foot = rent per year; divide by 12 for the month.
- TMI (taxes, maintenance and insurance) is your share of the building’s costs, charged the same way, per square foot per year.
- HST: a commercial lease is a taxable supply, so 13% HST is added to the rent in Ontario. A business registered for GST/HST may be able to claim it back as an input tax credit.
- Rent increases: the Commercial Tenancies Act does not regulate commercial rent increases. The lease sets them, usually as a step per square foot or a percentage each year.
Before you sign, read the 12 clauses to check in a commercial lease. New to the terms? Start with net lease vs gross lease, and what TMI means.
More for business owners: commercial leasing. All tools: all calculators.
Sources (official pages, checked October 4, 2026)
- CRA GST/HST Memorandum 19.4.1 – Commercial real property, sales and rentals (a commercial lease is a taxable supply)
- CRA – GST/HST rates (Ontario 13%)
- CRA – Input tax credits (rent for commercial activities)
- Ontario – Renting commercial property in Ontario (Commercial Tenancies Act, updated July 2, 2026)
Programs and limits change, often at budget time. Confirm the current rules on the official page before you rely on them.
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General information only – not financial, legal or mortgage advice. Please consult a licensed professional about your own situation.