How do you measure a room in square feet if it's not a perfect rectangle?

Split the floor plan into rectangular sections — an L-shaped room is usually two rectangles, a room with a bay window is a rectangle plus a smaller one. Measure the length and width of each section separately, calculate each one's square footage, then add the results together.

Do you measure square footage wall-to-wall or to the inside of the baseboards?

For flooring, paint, and most home-project purposes, measure wall-to-wall (or baseboard-to-baseboard) at floor level — that's the usable floor area. Real estate square footage sometimes uses exterior wall measurements instead, which is a different (larger) number; if you're comparing to a listing, check which method it used.

How do you convert square feet to square yards?

Divide square feet by 9 (since 1 square yard = 9 square feet). This matters most for carpet, which is often priced and sold by the square yard: a 150 sq ft room is about 16.7 square yards.

Do closets and alcoves count toward a room's square footage?

For flooring, paint, and furniture-planning purposes, yes — include any floor area you'll actually be covering or working with, closets included. Measure them as their own small rectangle and add that to the total.

How to Measure the Square Footage of a Room

Multiply the room's length by its width, both in feet, to get square feet. For an irregular room, split it into rectangles, find each one's square footage, and add them together.

Multiply a room’s length by its width, both measured in feet, to get its square footage. A 12 ft by 10 ft room is 120 square feet. If the room isn’t a simple rectangle, split it into smaller rectangles, find the square footage of each, and add them up.

The basic formula

Length (ft) × Width (ft) = Square footage

Measure wall-to-wall along the room’s longer wall for length, and along the shorter wall for width. Both measurements should be in feet — if your tape measure gives you feet and inches (like 12’6”), convert the inches to a decimal first: 6 inches is 0.5 ft, so 12’6” becomes 12.5 ft.

Example: A room measuring 14’3” by 11’ → 14.25 ft × 11 ft = 156.75 sq ft.

Measuring an irregular room

Most rooms aren’t perfect rectangles once you account for closets, bay windows, or an L-shaped layout. The fix is the same one you’d use for any odd shape: break it into rectangles.

Sketch the room from above, including every jog, closet, and alcove.
Draw straight lines across the sketch to divide it into rectangular sections — an L-shaped room typically splits into two rectangles; a room with a closet splits into the main room plus the closet.
Measure each section’s length and width separately.
Calculate each section’s square footage, then add all the sections together.

Example — an L-shaped room: Main area 15 ft × 12 ft (180 sq ft) plus an extension 6 ft × 5 ft (30 sq ft) → 210 sq ft total.

Wall-to-wall vs. exterior measurements

There are two common conventions, and they give different numbers:

Wall-to-wall (interior): measured from baseboard to baseboard at floor level. This is what you want for flooring, paint, rugs, and furniture planning — it’s the actual usable floor area.
Exterior: measured from the outside faces of the exterior walls, sometimes used in real estate listings and appraisals. This includes wall thickness and will always be a somewhat larger number than the interior measurement.

If you’re pricing flooring or paint, always use the interior measurement — a supplier quoting you based on exterior square footage will overestimate what you need.

Converting square feet to other units

Square yards (common for carpet pricing): divide square feet by 9.
Square meters: multiply square feet by 0.0929.

A quick sanity check

Once you have a total, it’s worth a rough gut-check: pace off the room and estimate its size by eye, or compare it to a room of known size in your home. A basic bedroom is typically 120–200 sq ft; if your calculation comes out wildly outside that range for a similarly-sized room, re-check your measurements before ordering materials.