Founders & Small BusinessFree tool
Commercial Lease Review and Cost Calculator
Paste your lease and see what it costs each year of the term, what the landlord can raise later, and which changes save the most.
Free to start · Opens in your River workspace, ready to edit and share
How to review a commercial lease
To review a commercial lease, read the whole lease and every exhibit against the terms you agreed to. Check the space you're charged for and who pays the building's costs, then total what the lease will cost over its full term. A good review gives you three things: the total cost, every date you must act by, and the changes worth asking for, ranked by dollars.
The quoted rent is where the cost starts, not where it ends. Operating expenses, build-out costs above the landlord's allowance and the duty to restore the space when you leave can all sit outside it. In the worked example below, they take a $32.00 quote to $58.51 a square foot a year.
Gather the whole lease first
A commercial lease is rarely one document. Before reading a clause, ask for every exhibit and the numbers behind them:
- The floor plan, showing rentable and usable area
- The work letter, which sets the allowance and who builds what
- The last three years of operating expenses and this year's budget
- The building rules and any personal guarantee you would sign
Then lay the lease beside the letter of intent, the short proposal in which you and the landlord agreed the main terms. Mark every place the lease differs or adds something new. Those marks are your first questions.
Check the space you're paying for
Rent is usually charged on rentable square feet, a bigger number than the space you can use. The US General Services Administration (GSA), which leases space for federal agencies, notes that rentable area is determined by the building owner and may vary by city or by building1. It can include a share of lobbies, corridors and restrooms.
The extra, as a share of the space you use, is the load factor, also called the common area factor. In GSA's own example, 10,000 square feet that the tenant occupies are billed as 11,500 rentable, a common area factor of 15%1. To find yours, divide rentable by usable square feet and subtract one. Then compare spaces on the cost per usable foot.
BOMA International, the association of building owners and managers, says its standards are considered the de facto building measurement standards2 in many US markets. It has separate versions for offices, retail and industrial space, each revised over the years, so ask which one the landlord used, and for the measured drawings.
Find out who pays the building's costs
In a net lease, Cornell's Legal Information Institute explains, the tenant pays the base rent plus some or all of the property's operating and maintenance expenses3. The common labels:
- Gross: one rent, and the landlord pays taxes, insurance and upkeep
- Gross with a base year: one rent, plus your share of any rise in costs above a base year
- Single or double net: base rent plus taxes, or taxes and insurance
- Triple net (NNN): base rent plus taxes, insurance and common-area maintenance
Labels vary, so read what the lease actually passes on. Check your share as a percentage of the building. Then ask to exclude costs that belong to the landlord, such as its loan payments, commissions for leasing other space and rebuilding the roof or structure.
Ask for two protections: a cap on yearly increases in the costs the landlord controls, and the right to audit its books. If heating and cooling fall to you, ask whether that includes replacing the equipment, not just repairing it.
Total the cost over the full term
Put every charge into one model, with a row for each year. Grow base rent by the increases the lease states, and operating expenses by what they have actually done. Add one-off costs in the year they land.
The quote: 4,200 rentable square feet (3,650 usable) at $32.00 a foot a year, triple net, for seven years. Rent rises 3.5% a year, and the first three months are free.
Base rent: $1,011,952 over the term, after $33,600 of free rent.
Operating expenses: $393,259, starting at $11.50 a foot and growing 5% a year, due in the free months too.
Build-out: $239,400 above the allowance, because the work costs $92 a rentable foot and the allowance pays $35.
Restoring the space at the end: about $75,600, estimated at $18 a foot.
Total: $1,720,211. That is $58.51 per rentable foot a year, or $67.33 per usable foot, against the $32.00 quoted.
- Free rent is worth less than it looks. The three free months save $33,600 of rent, but $12,075 of expenses is still due.
- The allowance is not the cost. The other $57 a foot is yours, spent in a building you don't own.
- Price what has no price. The lease states the duty to restore, not its cost, so estimate it.
Run every space you're considering through the same model and compare totals, not quotes. A low rent with a thin allowance can still cost more overall. Then use a cash flow forecast to check you can pay for the build-out and the first months of rent.
Review the clauses that cost you later
These terms carry no price, but they decide what you owe when plans change.
Terms that cost money later
| Clause | What to check | A reasonable ask |
|---|---|---|
| Personal guarantee | Whether you personally owe the rent if the company can't pay | A cap, such as a year's rent, that ends after two years of on-time rent |
| Assignment and subletting | Whether you can sublet or sell the business. If you sublet, you still owe the lease4 | Consent not unreasonably withheld, and none needed for a sale or merger |
| Renewal option | The window for giving notice, and how the new rent is set | A wide notice window and a capped renewal rent |
| Holdover | What you owe if you stay past the end. Staying on can even bind you to a new lease5 in some states | A modest rent premium for the first 60 days, and no claim for the landlord's other losses |
| Restoration | What you must remove when you leave, and the condition you hand back | A list, agreed now, of anything that must come out |
Confirm you can legally run your business there. The US Small Business Administration warns that zoning ordinances can restrict or entirely ban specific kinds of businesses6 in an area, and suggests asking the city planning office.
If the public will visit, as in a shop, clinic or restaurant, read who handles accessibility. The Justice Department says landlord and tenant both have full responsibility for complying7 with the Americans with Disabilities Act. A lease can split the work, but the split binds only the two of you.
Negotiate with numbers, then sign
Rank your asks by the dollars each one moves over the term. In the example above:
- No duty to restore the space at the end: $75,600
- An allowance $10 a foot higher: $42,000
- Starting rent $1 a foot lower: about $31,600
- A 3% yearly cap on operating expense growth: up to $23,200
- A fourth free month: $11,200
Send each ask in writing, with its reason and its number. Check every new draft against your last version; a redline comparison lines up each round for you.
When to bring in a lawyer
Have a real estate lawyer read the final draft before you sign, especially with a personal guarantee, a long term or a large build-out. Whether a clause is enforceable depends on state and local law. This guide is general information for US readers, not legal advice.
Before you sign the lease
- Rent, term, allowance and free months match the letter of intent
- Every exhibit the lease mentions is attached
- You know the rentable and usable area, and how they were measured
- You've totaled the cost of every year, not just the first
- Zoning allows your use, and the lease says who handles accessibility
- You know every notice deadline and the date it is counted from
Once it is signed, keep those dates in a contract renewal tracker. To run this review on your own lease, paste it into the tool at the top of this page.
How it works
Paste your lease, or attach it with its exhibits, and say what you'll do in the space. River reads it and builds two things in your workspace. A sheet gives the cost of each lease year, the dates you must act by and the changes worth asking for, ranked by dollars. A report sets the quoted rent beside the true cost per square foot and shows which costs the landlord can raise later. It also lists any exhibit the lease mentions that you haven't sent.
Where a number is missing, such as the usable area or the build-out price, River estimates it, labels the estimate and shows how the total moves if it is wrong. Anything else it can't confirm is marked for you to check. It never says whether a clause is enforceable, and it never contacts your landlord. For the other contracts you sign, use the contract review for founders.
Share your lease
Paste or attach the lease with its exhibits, and say what you'll do in the space.
River totals the term
It models every lease year: rent increases, operating expenses, free months, the build-out gap and restoration.
Get the true cost
A cost sheet and a report: the true cost per square foot, key dates and asks ranked by dollars.
Negotiate with numbers
Edit anything, compare a second space, or ask River to draft your requests to the landlord.
What you get
- The cost of every lease year, with base rent, operating expenses and one-off costs in separate columns
- The quoted rent beside the true cost per rentable square foot, and the total over the term
- A split between the costs the lease fixes and the costs the landlord or others can set later
- The gap between the improvement allowance and your build-out, plus the cost of restoring the space
- Every date you must act by, such as renewal notice deadlines, worked out from the start date
- The changes worth asking for, ranked by the dollars each one moves over the full term
Common questions
What should I look for when reviewing a commercial lease?
When reviewing a commercial lease, look first at the total cost, not the rent. That means base rent and its increases, your share of operating expenses, the build-out above the allowance and any duty to restore the space. Then read the terms that bite later, such as the personal guarantee, subletting, the renewal notice window and holdover. Finally, check that every exhibit is attached.
What is a triple net lease?
A triple net lease is one where you pay base rent plus your share of the property's taxes, insurance and common-area maintenance. Those costs can rise every year. Before you sign, ask for the last three years of actual figures, this year's budget and a cap on how fast the costs the landlord controls can grow.
What is a load factor in a commercial lease?
A load factor is the share of common space, such as lobbies, corridors and restrooms, added to the space you occupy to give the rentable area you pay rent on. For example, if you rent 4,200 square feet but can use 3,650, you pay for 550 square feet of shared space. That is a load factor of about 15%, since 550 is 15% of 3,650.
How do I review a commercial lease with River?
Paste your lease into the box at the top of this page, or attach it with its exhibits, and say what you'll do in the space. River totals the cost of every year of the term, dates each deadline and ranks the changes worth asking for. The sheet and report open in your free River workspace, ready to edit.
Do I need a lawyer to review a commercial lease?
Not by law, but it is worth it for any lease you plan to sign. A real estate lawyer can tell you whether a clause will hold up where you are and can redraft the wording you want changed. Work out the cost and list your questions first, so their time goes on the clauses that carry real risk rather than on arithmetic.
Can River review a lease I've already signed?
Yes. Pick the option for a lease you've already signed, and River works out what each year of the term will cost you. It also dates every deadline, such as the renewal notice window, from your start date. If rent is squeezing your cash, the cost reduction plan weighs it against your other possible cuts.
Is the commercial lease review tool free?
Yes, it is free to start. Your cost sheet and report open in a River workspace, where you can edit them, share them or ask River to change them. Paid plans add more AI use and access to the most advanced models.
Sources
U.S. General Services Administration. “Class Deviation CD-2023-03: Lease Definitions Clause.” gsa.gov (opens in a new tab)
BOMA International. “BOMA Standards.” boma.org (opens in a new tab)
Cornell Law School. “net lease.” law.cornell.edu (opens in a new tab)
Cornell Law School. “sublease.” law.cornell.edu (opens in a new tab)
Cornell Law School. “holdover tenant.” law.cornell.edu (opens in a new tab)
U.S. Small Business Administration. “Launch your business.” sba.gov (opens in a new tab)
U.S. Department of Justice. “ADA Title III Technical Assistance Manual.” ada.gov (opens in a new tab)
Built by
Chandler Supple
Co-founder & CEO, River
Chandler has spent the last six years working in AI, building tools for millions of users and Fortune 100 companies. In 2025, he co-founded River to build a new kind of operating system for AI agents.