How this instrument works
Net effective rent (NER) takes the rent a listing advertises and the free months a landlord throws in, then averages the two into one honest monthly figure. It does this by dividing the total dollars actually owed over the whole lease by the whole lease term — including the free months, which count as zero-dollar months inside that average. That last detail matters: dividing total rent by only the months you pay would just hand you back the stated rent and tell you nothing new. NER only works as a comparison tool because the free months stay in the denominator.
Leasing agents quote a face rent to keep a listing looking competitive against comparable units, then close the gap with a concession — a free month, six weeks off, a reduced first quarter — rather than lowering the advertised number itself. Apartment hunters comparing two buildings, commercial tenants sizing an office suite, and portfolio managers reporting a building's real income to owners or lenders all reach for net effective rent for the same reason: face rent tells you what a unit is listed at, not what it actually costs to occupy for a year.
The figure this returns is a simple average, not a discounted one — it treats a free month at lease signing exactly the same as a free month in the final week, even though money handed back sooner is worth more to whoever receives it. It also excludes anything the concession itself does not touch: a security deposit, a broker fee, tenant-improvement dollars, or the rent reset that often follows once a promotional term ends. Those sit outside this arithmetic and belong in a separate line-by-line comparison of the two leases.
- Enter the advertised figure in Stated monthly rent, $ — the number on the listing or the lease's face page.
- Enter Lease term, months — the full length of the agreement the concession is spread across.
- Enter Free (concession) months — how many months of rent the landlord is waiving, in whole or half months.
- Read Net effective rent, $/month — the true average cost, ready to set beside a second offer with a different rent-and-concession mix.
Worked example — a $2,000 unit with one month free
A listing quotes $2,000 a month on a 12-month lease with one month free as the signing concession. Total rent actually owed over the year is $2,000 times eleven paid months, $22,000, and spreading that across all twelve months of the term gives a net effective rent of $1,833.33 — about $167 a month below the number on the listing, even though nobody's stated rent ever changed.
Compare that against a second listing offering the identical $2,000 face rent and one free month, but on a 24-month lease instead of twelve. The same one-month concession now dilutes across twice as many months, landing at $1,916.67 — nearly a full $83 higher than the shorter lease despite an identical headline deal. Longer terms make any fixed concession look smaller once it is averaged out, which is exactly why landlords often reserve their best free-month offers for the leases they most want signed quickly.
Questions
Why isn't net effective rent just the stated rent minus a monthly average of the free rent?
It is, but the averaging has to happen across the full lease term, not across the months you actually pay. Dividing the total dollars owed by only the paid months returns the stated rent exactly and erases the concession from the math — the free months have to stay in the denominator for the comparison to mean anything.
Why would a landlord offer free months instead of just lowering the rent?
A lower face rent becomes the new baseline for every future renewal, rent survey, and comparable-property valuation tied to that unit. A temporary concession moves the same dollars off the books without resetting the number everyone else — appraisers, lenders, future tenants comparing listings — sees as the asking rent.
Does a free month at the start of a lease save more than one at the end?
Not in this formula — it treats every free month identically regardless of when it lands, because it is a simple average, not a discounted one. In practice a concession received sooner is worth more, since that money can be spent, saved, or invested earlier; this instrument does not adjust for that timing difference.
Should I compare net effective rent between an apartment and an office lease the same way?
The averaging math is identical either way, but read the inputs consistently: residential listings usually quote one flat monthly figure, while commercial space is often quoted per square foot per year with taxes and maintenance billed separately. Convert a commercial quote to a single monthly rent figure before entering it here.
What does this number leave out of the real cost of moving in?
It leaves out the security deposit, any broker or application fee, moving costs, and what the rent resets to once the concession period ends and the lease rolls to its stated rate. Those are one-time or later costs the concession itself does not touch, and they belong in a separate comparison alongside this monthly figure.
Why do property owners and lenders care about net effective rent for a whole building?
Asking rent across a portfolio can look flat or rising even while landlords quietly hand out heavier concessions to fill units — a pattern common when vacancy climbs. Net effective rent strips that gap out and shows the income a building is actually collecting, which is the figure appraisers and lenders weigh more heavily than the advertised rate.
References
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.