Apartment Square Footage Calculator
Enter the gross and usable square footage on the left, and the right side shows the efficiency ratio, the square feet you lose to walls and shared space, the m² equivalent, and — if you add a price — the cost per square foot.
Area input
Area
Price (optional)
Enter the gross and usable square footage to see the efficiency and areas.
Area analysis
Results convert your figures at 1 m² = 10.7639 sq ft and are for reference only; actual square footage depends on the measuring standard (ANSI Z765-2021 for detached homes measures to the exterior walls, while condos are measured to interior faces), so listings and appraisals can differ. Always confirm the measured square footage and what it includes before making an offer.
ready to use.
- Visible firstKeep the input and result positions clear.
- Results firstPut the main number up front and keep the process secondary.
- Less to askNo sign-up or extra information before using the tool.
How to read usable space from gross square footage
Square footage is confusing because the number in the listing is not always the space you actually live in. Two units can both be "1,100 sq ft" yet feel very different, because one figure may be gross (measured to the outside walls or including a share of common areas) and the other usable (the interior you can furnish).
This tool takes the gross and usable square footage and instantly shows the efficiency ratio, how much you lose to walls and shared space, the square meters equivalent, and the price per square foot — so you can compare listings on the space you actually get, not just the headline number.
Gross vs. usable square footage
Gross square footage is the larger, advertised figure — for condos it often folds in a share of hallways, lobbies, and mechanical space, and under ANSI Z765 detached homes are measured to the exterior faces of the outer walls. Usable (net) square footage is the interior living space you can actually furnish. The gap is real estate you pay for but cannot use.
- Gross = advertised area, measured to exterior walls or including a share of common space
- Usable / net = the interior living space you can furnish
- The difference is walls, hallways, elevators, and shared areas
What to enter and how to read it
Enter the gross square footage and the usable square footage on the left. The quick-input chips (Studio / 1BR / 2BR / 3BR) fill in typical gross and usable figures. On the right you see gross and usable side by side, then the efficiency ratio, a usable-vs-loss bar, and the square feet lost. Add a price and it also computes the price per gross square foot, per usable square foot, and per square meter.
- Enter gross and usable square feet from the listing or floor plan
- The chips auto-fill representative gross / usable figures
- If usable is larger than gross it flags an input error (check the values)
- Price is optional — add it for price-per-sq-ft figures
Converting square feet to square meters
Most of the world lists homes in square meters, so converting is useful when comparing internationally or reading imported specs. One square meter equals 10.7639 square feet, so to go from square feet to square meters you divide by 10.7639. For example, 1,100 sq ft ≈ 102.2 m², and 750 sq ft ≈ 69.7 m². This tool shows the m² equivalent next to every figure.
- 1 m² = 10.7639 sq ft
- sq ft ÷ 10.7639 = m²
- 1,100 sq ft ≈ 102.2 m² / 750 sq ft ≈ 69.7 m² (example)
What the efficiency ratio means
The efficiency ratio is the usable area divided by the gross area (usable ÷ gross × 100). It is the inverse of the "loss factor" used in real estate: a 15% loss factor means 85% efficiency. The higher the efficiency, the more of the advertised space you actually live in. High-rise condos with large amenity floors, and older buildings with thick walls and long corridors, tend to have lower efficiency.
- Efficiency = usable ÷ gross × 100
- Loss factor = 100% − efficiency
- Higher efficiency = more of the advertised space is usable
Reading the usable-vs-loss bar
The bar on the right splits the gross area into usable (dark) and lost (light). The dark length is the efficiency. What is hard to picture from numbers alone — how much of the advertised area is walls and common space — becomes obvious. When comparing two units, compare the dark share to see which one gives you more real living space for the same headline size.
How price per square foot is calculated
Price per square foot is the price divided by the square footage, and it is the standard way to compare homes. This tool divides the price by the gross square footage for the headline figure, and also by the usable square footage — which is the more honest number, because that is the space you actually use. For example, $750,000 on 1,100 gross sq ft is about $682/sq ft, but about $802 per usable sq ft. Comparing on price per usable square foot is fairer across buildings with different loss factors.
- Price per gross sq ft = price ÷ gross square footage
- Price per usable sq ft = price ÷ usable square footage
- Compare buildings on price per usable sq ft for a fair comparison
Balconies, garages, and what does not count
Under the ANSI Z765 standard, gross living area (GLA) counts only finished, heated space that is at or above grade. Balconies, patios, garages, and unfinished basements are not part of the square footage, even though they add value. So two units listed at the same square footage can differ a lot in real usability depending on outdoor and storage space. Confirm what is and is not included before comparing.
The trap of the headline square footage
A single "1,100 sq ft" number hides whether it is gross or usable, and whether a share of common area is baked in — a practice especially common with condos in dense markets like New York, where advertised square footage can be well above the usable interior. Do not trust the headline figure alone; ask for the measured interior square footage and the standard used.
Common mistakes
The most common errors are mixing up gross and usable figures, comparing a gross number in one listing to a usable number in another, or comparing square footage measured under different standards. If a listing says "1,100 sq ft gross / 935 sq ft interior," enter each in its own field so the efficiency comes out right. Checking the list below reduces mismatches with the real documents.
- Did you avoid swapping the gross and usable figures?
- Are you comparing like-for-like (both gross, or both usable)?
- Is usable ≤ gross (if usable is larger, it is an input error)?
- Did you exclude balconies, garages, and unfinished space?
Before you make an offer
Square footage drives price, taxes, and comparisons, so use the results as a guide but confirm with the real documents before you commit. Checking the points below reduces the gap between the listing and reality.
- Did you confirm the measured square footage and the standard used (ANSI Z765)?
- Did you compare units with similar efficiency for real living space?
- Did you compare price per usable square foot across buildings?
- Did you separate balconies, storage, and parking from the living area?
- For taxes and financing, did you confirm which square-footage figure applies?
Apartment square footage — frequently asked questions
What is the difference between gross and usable square footage?
Gross square footage is the larger, advertised figure — measured to the exterior walls or, for many condos, including a share of common areas like hallways and lobbies. Usable (net) square footage is the interior space you can actually furnish. The difference is walls and shared space that you pay for but cannot use, so always check which figure a listing is quoting.
How do I convert square feet to square meters?
One square meter equals 10.7639 square feet, so divide the square feet by 10.7639 to get square meters. For example, 1,100 sq ft is about 102.2 m². This tool shows the m² equivalent next to each figure automatically, which is handy when comparing to metric listings.
What efficiency ratio is good?
Most apartments and condos land around 80–90% efficiency (a 10–20% loss factor). Higher is generally better because more of the advertised space is usable, but buildings with large amenity floors or thick walls run lower. Rather than a fixed target, compare the efficiency of similar units to see which gives you more real space for the money.
Should I compare price per gross or per usable square foot?
Listings usually quote price per gross square foot, and this tool shows that. But price per usable square foot is the more honest comparison, because that is the space you actually live in. Two units at the same price per gross sq ft can differ a lot per usable sq ft if their loss factors differ, so pick one basis and use it consistently.
Do balconies count toward square footage?
No. Under the ANSI Z765 standard, only finished, above-grade interior space counts as gross living area. Balconies, patios, garages, and unfinished basements are excluded even though they add value. So confirm outdoor and storage space separately — two units with the same square footage can offer very different real usability.
Reference date: 2026-07-18. Conversions use 1 m² = 10.7639 sq ft; efficiency = usable ÷ gross × 100. Residential square footage follows the ANSI Z765-2021 standard.