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How to Measure the Square Footage of a Room

Measuring square footage is straightforward for rectangular rooms: length times width in feet. For L-shapes, closets, or irregular spaces, break the area into rectangles and add them up.

Chris Terry
By Chris Terry, Founder & Editor
Updated June 17, 2026

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To measure a room's square footage: use a tape measure to record the length and width in feet, then multiply them together. A 12-foot by 15-foot room is 180 square feet (12 x 15 = 180). For rooms that are not a simple rectangle, divide the space into separate rectangles, calculate each one, and add the totals.

What you need

How to measure a rectangular room

  1. Measure the longest wall from corner to corner. Write it down.
  2. Measure the adjacent wall (perpendicular to the first). Write it down.
  3. Multiply: length x width = square feet.
  4. Example: 13 ft x 11 ft = 143 sq ft.

How to measure an L-shaped room

Split the L into two rectangles. Measure each rectangle separately and add the two results. For example, an L-shaped living room might be a 12x18 section (216 sq ft) plus an 8x10 section (80 sq ft), for a total of 296 square feet. Use our square footage calculator to handle L-shaped and multi-section rooms automatically.

Common room square footages for reference

Room dimensionsSquare footage
10 x 10100 sq ft
10 x 12120 sq ft
12 x 12144 sq ft
12 x 15180 sq ft
14 x 14196 sq ft
15 x 20300 sq ft

Measuring for flooring vs. painting

For flooring, measure the floor area only (length x width of the floor). For painting, you need wall area: measure the room perimeter (add all four walls) and multiply by ceiling height, then subtract doors and windows. These are two different calculations from the same room dimensions. See how much flooring to order and how much paint to buy for the next steps after measuring.

Measuring in inches and converting

If your tape shows inches: divide each measurement by 12 to convert to feet. A room that measures 147 inches by 168 inches is 12.25 feet by 14 feet, or about 171.5 square feet. It is easier to measure directly in feet by reading the large numbers on the tape and estimating the fraction of a foot for the remaining inches.

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Good to know

FAQs

How do you calculate square footage of a room?

Multiply the room length by the room width, both measured in feet. The result is square feet. A 13x11 room is 143 square feet. For non-rectangular rooms, divide the space into rectangles, calculate each, and add the areas.

How do I measure square footage of an L-shaped room?

Divide the L-shape into two rectangles. Measure each rectangle's length and width, calculate the area of each (length x width), and add the two totals. For example, a 10x15 section plus a 10x8 section is 150 + 80 = 230 square feet.

Is square footage length times width?

Yes, for any rectangular space. Square footage equals length (in feet) multiplied by width (in feet). The word 'square' refers to the unit (square feet), not the shape of the room.

How accurate does my square footage measurement need to be?

For flooring and tile, within 1 to 2 inches is fine since you are adding a 10 percent waste buffer. For paint, rough measurements are adequate because coverage estimates already have some variability built in. Measure at least twice and use the average if you get different readings.