How is apartment square footage measured?

Usually from the inside. Measure along the inside faces of the unit's perimeter walls (the walls shared with neighbors, the corridor and the outside), calculate the area they enclose, and leave out balconies, storage outside the unit and parking. This is the interior perimeter approach Fannie Mae uses for condo and co-op apartment units. A building may also quote a larger rentable figure that adds a share of common areas, so check which one you're looking at.

Does ANSI Z765 apply to apartments or condos?

No. ANSI Z765, the US standard for measuring homes, covers detached and attached single-family houses only, not apartment or multifamily buildings. Fannie Mae has condo and co-op apartment units measured by their interior perimeter instead, and Freddie Mac's ANSI requirement excludes apartment-style condo and co-op units. Townhouses and rowhouses are attached single-family homes, which ANSI does cover.

What is the difference between rentable and usable square footage?

Usable area is the space inside the unit that the occupant actually uses. Rentable area is usable area plus a share of the building's common areas, such as corridors, lobbies and amenity space, allocated to each unit, so it is always the larger number. The terms come from commercial leasing; BOMA International publishes measurement standards for office and multifamily buildings that define them in detail.

Do balconies count in apartment square footage?

Not in the unit's interior area. Balconies, patios and terraces are outdoor space, so measure and list them separately (for example, 804 sq ft plus a 60 sq ft balcony). The same goes for storage lockers and parking outside the unit.

Why is my apartment smaller than the advertised square footage?

The advertised figure may be rentable area, which includes a share of common space, or it may have been measured to the outside of the walls or taken from the developer's plans rather than the finished unit. It may also include a balcony. Ask how the figure was measured; an interior measurement of the unit will usually be the smallest of these numbers.

How do I estimate paint and flooring for an apartment turnover?

Measure each room's floor area and perimeter. For flooring, add the floor areas, add about 10% waste for a straight layout, and divide by the box size. For paint, multiply each room's perimeter by the ceiling height, subtract doors and windows, multiply by the number of coats, and divide by the coverage on the can, typically about 350–400 sq ft per gallon. A one-bedroom unit with 847 sq ft of wall takes about 4.2–4.8 gallons for two coats.

Guide

How to Measure Apartment Square Footage

How apartment square footage is measured, why rentable and usable area differ, and how to get accurate numbers for listings and unit turns.

Updated October 12, 2026 · FloorFigures

Short answer

Apartments are usually measured inside: along the inside faces of the unit's perimeter walls, counting the area they enclose and leaving out balconies and storage. ANSI Z765, the standard for houses, doesn't apply to apartment buildings, and Fannie Mae has condo units measured by their interior perimeter. A building may also quote rentable area, which adds a share of corridors and other common space, so say which figure you're listing.

A house has a well-known measuring standard. An apartment doesn't have one that everyone follows, which is why two units with the same advertised size can feel very different, and why a tenant with a tape measure may find less than the listing promised. Here's what the standards do and don't cover, how to measure a unit yourself, and how to turn the same measurements into a paint and flooring estimate for a unit turn.

Is there a standard for apartment square footage?

Standard or rule	What it says about apartments
ANSI Z765-2021	Covers detached and attached single-family houses only, not apartment or multifamily buildings
Fannie Mae appraisals	Condo and co-op apartment units are measured by their interior perimeter; ANSI isn't required for 2–4 unit properties
Freddie Mac appraisals	ANSI required for one-unit properties, excluding apartment-style condo and co-op units
BOMA International	Publishes measurement standards for office and multifamily buildings, including rentable area
Local rules	Your state or city may have its own rules on advertising area; check yours

Townhouses and rowhouses are different: they're attached single-family homes, which ANSI Z765 covers, measured to the exterior finished surface (or to the centerline between houses where appropriate). See ANSI Z765 explained and Fannie Mae's ANSI requirement.

Rentable vs usable square footage

These terms come from commercial leasing, and some multifamily owners use them too. As general concepts:

Figure	What it generally means	Where you'll see it
Usable (interior) area	The floor inside the unit, to the inside faces of its perimeter walls	Condo appraisals, interior-measured listings
Rentable area	Usable area plus a share of common areas (corridors, lobbies, amenity space) allocated to the unit	Leases and marketing in some buildings
Plan or marketing area	Whatever basis the developer's plans used, which may be to wall centerlines or outside faces	Brochures and websites
Gross building area	The whole building, measured outside	Building-level figures, not individual units

How to measure an apartment unit

Sketch the unit's outline, including any notches and bump-outs.
Measure along the inside faces of the perimeter walls: the walls shared with neighbors, the corridor and the outside. Wall to wall, to the nearest inch.
Calculate the enclosed area. Split the outline into rectangles and add them. Interior partitions are inside the perimeter, so in an interior perimeter measurement you typically don't subtract them.
Leave out what's outside the unit: balconies, patios, storage lockers and parking. List them separately.
For a two-level unit, measure each level, counting a stair opening once, on the lower floor.
Round the total to the whole square foot and write down how you measured.

A worked example, for a one-bedroom unit with a notch at the entry:

Piece	Dimensions	Area
Unit outline, inside faces	34'6" × 24'0"	828 sq ft
Less: entry notch (corridor side)	6'0" × 4'0"	−24 sq ft
Interior area		804 sq ft
Balcony (listed separately)	10'0" × 6'0"	60 sq ft

For irregular outlines, see L-shaped and irregular rooms.

Listing a unit's square footage

Say what the number is: "804 sq ft, measured to the inside faces of the unit's walls; 60 sq ft balcony." One line removes most disputes.
Use one method across the portfolio, so identical floor plans show identical sizes.
Don't copy a developer's figure without knowing whether it's interior, rentable or measured to the outside.
Check local rules on advertising rental square footage, and keep the listing consistent with your lease.

Estimating a unit turn: paint and flooring

The measurements you take for a listing also drive the turnover estimate. Here are the main rooms of the same one-bedroom unit, with 8 ft ceilings. Wall area is perimeter × height, minus the actual openings: a 3'0" × 6'8" door is 20 sq ft, a 3' × 5' window 15 sq ft and a 6'0" × 6'8" closet door 40 sq ft.

Room	Size	Floor	Perimeter	Walls less openings
Living room	15'0" × 13'0"	195 sq ft	56 ft	448 − 20 (door) − 30 (2 windows) = 398 sq ft
Bedroom	12'0" × 11'0"	132 sq ft	46 ft	368 − 20 (door) − 15 (window) − 40 (closet) = 293 sq ft
Hall	10'0" × 3'6"	35 sq ft	27 ft	216 − 60 (3 doors) = 156 sq ft
Kitchen	10'0" × 8'0"	80 sq ft	36 ft	Not painted (cabinets)
Total		442 sq ft		847 sq ft

Flooring

Luxury vinyl plank through all four rooms: 442 sq ft + 10% waste = 486.2 sq ft. At 20 sq ft per box, that's 24.3, so 25 boxes. Box coverage varies by product (roughly 17–30 sq ft), so use the number on yours. If the bedroom gets carpet instead, it's 11 ft wide, so one width of 12 ft broadloom (the most common roll width) covers it without a seam. Carpet is cut from the roll and priced by the square yard, so you pay for the full width: a 12' × 12' piece is 16 sq yd before any trimming allowance, against 14.7 sq yd of floor. Try the flooring calculator, LVP calculator or carpet calculator.

Paint

Two coats on 847 sq ft of wall is 1,694 sq ft of coverage. Sherwin-Williams says a gallon typically covers about 350–400 sq ft, which gives 4.2–4.8 gallons, so a 5-gallon pail covers it. Ceilings are extra: the ceiling area equals the floor area, 442 sq ft here. Use the paint calculator or the wall area calculator, and see how much paint you need for the method.

Measuring units in FloorFigures

FloorFigures is a free floor plan measuring tool with no limits, which matters when you have dozens of units. Open a unit's floor plan (a PDF from the building's drawings, an image, or a photo of a printed plan), set the scale, and press A to find every room. Each room gets its floor area and perimeter, wall area less openings, flooring with waste and boxes, and paint gallons. The defaults are 10% waste, 20 sq ft per box, 350 sq ft per gallon and 2 coats, all adjustable. Export the room schedule as a CSV for your turn checklist. Plans stay on your device.

Questions

How is apartment square footage measured?: Usually from the inside. Measure along the inside faces of the unit's perimeter walls (the walls shared with neighbors, the corridor and the outside), calculate the area they enclose, and leave out balconies, storage outside the unit and parking. This is the interior perimeter approach Fannie Mae uses for condo and co-op apartment units. A building may also quote a larger rentable figure that adds a share of common areas, so check which one you're looking at.
Does ANSI Z765 apply to apartments or condos?: No. ANSI Z765, the US standard for measuring homes, covers detached and attached single-family houses only, not apartment or multifamily buildings. Fannie Mae has condo and co-op apartment units measured by their interior perimeter instead, and Freddie Mac's ANSI requirement excludes apartment-style condo and co-op units. Townhouses and rowhouses are attached single-family homes, which ANSI does cover.
What is the difference between rentable and usable square footage?: Usable area is the space inside the unit that the occupant actually uses. Rentable area is usable area plus a share of the building's common areas, such as corridors, lobbies and amenity space, allocated to each unit, so it is always the larger number. The terms come from commercial leasing; BOMA International publishes measurement standards for office and multifamily buildings that define them in detail.
Do balconies count in apartment square footage?: Not in the unit's interior area. Balconies, patios and terraces are outdoor space, so measure and list them separately (for example, 804 sq ft plus a 60 sq ft balcony). The same goes for storage lockers and parking outside the unit.
Why is my apartment smaller than the advertised square footage?: The advertised figure may be rentable area, which includes a share of common space, or it may have been measured to the outside of the walls or taken from the developer's plans rather than the finished unit. It may also include a balcony. Ask how the figure was measured; an interior measurement of the unit will usually be the smallest of these numbers.
How do I estimate paint and flooring for an apartment turnover?: Measure each room's floor area and perimeter. For flooring, add the floor areas, add about 10% waste for a straight layout, and divide by the box size. For paint, multiply each room's perimeter by the ceiling height, subtract doors and windows, multiply by the number of coats, and divide by the coverage on the can, typically about 350–400 sq ft per gallon. A one-bedroom unit with 847 sq ft of wall takes about 4.2–4.8 gallons for two coats.