NRSF is net rentable square feet, the floor area inside your units that a tenant can rent. It leaves out the hallways, office, restrooms, elevator lobbies and mechanical rooms that sit inside the building but never appear on a rent roll.
Gross square feet is the whole building. NRSF is the part that earns rent. Occupancy, rent per foot and price per foot only mean something when you quote them on the second number.
How NRSF differs from gross square feet
Picture a 50,000 square foot building. Walk it with a tape and you'll find the units, plus everything that gets a tenant to the units. The corridors, the lobby, the manager's office and the panel room all count in the 50,000. None of them count in NRSF.
That's why two buildings of the same gross size can hold very different amounts of rentable space. A single-story drive-up site loses less to circulation than a multi-story conversion with wide corridors and a large lobby.
Conversions also show that NRSF isn't fixed. Inside Self-Storage points out that old buildings often have oversized elevator lobbies, stairwells and electrical rooms that can be redesigned into units (Inside Self-Storage). Every foot you reclaim moves from gross-only to rentable.
Why your occupancy belongs on NRSF, like the REITs report it
Public Storage reports its owned portfolio on a net rentable basis. At the end of 2025 that was about 229.4 million NRSF across 3,171 facilities (Public Storage 2025 10-K).
It measures performance on the same base. Same-store square-foot occupancy averaged 92.0% in 2025, and realized annual rent per occupied square foot was $22.54 (Public Storage 2025 10-K).
Notice the units. That rent figure is annual and per foot. Divide by 12 and it's about $1.88 a month, which is how most operators say it.
Your market and unit mix aren't theirs, so don't read it as a target. What's worth copying is the base. Their occupancy and their rent are both on rentable feet.
A worked example on 50,000 gross square feet
Assume a 50,000 square foot building with 42,500 NRSF. The other 7,500 is corridors, office and mechanical space. That makes NRSF 85% of the gross.
Assume units rent at $1.20 per NRSF per month and the building is 92% occupied by square foot. Swap in your own numbers.
| Measure | Result |
|---|---|
| Gross square feet | 50,000 |
| NRSF | 42,500 |
| Gross potential rent per month at $1.20 per NRSF | $51,000 |
| Occupied NRSF at 92% | 39,100 |
| Rent from occupied space per month | $46,920 |
Now the mistakes. Divide that $51,000 by gross square feet and you get $1.02 a foot, not $1.20. You'd think your rates were lower than they are, and you'd compare yourself to the wrong competitors.
Divide the 39,100 occupied feet by 50,000 gross and occupancy reads 78.2%. The building didn't lose nearly 14 points of tenants. The measure just counted the hallways as vacant units.
Both errors come from one habit, which is mixing a gross number into a rentable ratio. If you want the next layer, physical vs economic occupancy covers what happens once you price the occupied space.
How to find your NRSF
Your rent roll is the best source. Add up the square footage of every unit, occupied or vacant. A 10x10 is 100 feet and a 5x10 is 50. The total is your NRSF.
Your site plan or the architect's area schedule shows the gross. The difference between them is your non-rentable space.
If your management software reports a different total than the unit list, find out why. It could be a unit that was combined or split and never updated, or outside parking carried as a unit type. Ask what's counted whenever someone quotes you a square footage, including a broker, a lender or a vendor.
What to do this week
- Export your unit list with each unit's dimensions and status.
- Multiply length by width for every unit and total it. That's your NRSF.
- Compare it to the NRSF your software, your appraisal and your listings use. Write down every mismatch and why.
- Divide occupied NRSF by total NRSF for physical occupancy. Divide monthly rent from occupied units by occupied NRSF for rent per NRSF.
- Pull your street rates the same way, per NRSF per month, so a 5x5 and a 10x20 can sit on one line.
- Rerun your rate and ad targets on the corrected number.
Mistakes that cost money
Quoting gross in a deal. A price per foot on gross area looks cheaper than it is. Buyers and sellers should both say which base they used.
Counting a unit twice. A split or merged unit that stays on the books twice overstates NRSF and understates occupancy.
Leaving reclaimed space out. If you converted a storage room or a former office into units, add it. Your rent per NRSF and occupancy were being measured against the old, smaller number.
Comparing across bases. Your occupancy is on units, a competitor's is on feet, and a broker's is on gross. Convert before you compare.
Get the NRSF right first. Every rate and ad target you set sits on it, and your move-ins and marketing results only compare cleanly on the same base. For the rate side of the same math, how an ECRI pays off is the next read.