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How do I calculate the square footage of a room?

Short answer

Measure the length and width in feet and multiply them: a 12 ft by 10 ft room is 120 square feet. For L-shaped or irregular rooms, split the space into rectangles, calculate each one, and add them up. A free room area calculator does the multiplication and the unit conversions instantly.

Rectangles first, everything else is rectangles added together

Area = length x width, so 15 ft by 12 ft is 180 square feet. An L-shaped room is just two rectangles: measure each section separately and add the results. Measure at floor level along the walls, and keep all measurements in feet (convert inches to decimals, so 6 inches is 0.5 ft) before multiplying.

Why the number matters

Square footage drives flooring and paint quantities, rent and sale price comparisons, and heater or air conditioner sizing. If you need metric, one square meter is about 10.764 square feet, so a 120 sq ft room is about 11.15 square meters. When ordering materials, it is common practice to add roughly 10 percent for cuts and waste.

Step by step

  1. Measure the length. Measure the longest wall in feet at floor level.
  2. Measure the width. Measure the perpendicular wall the same way.
  3. Multiply, and add sections. Multiply length by width. For irregular rooms, repeat per rectangular section and add the areas together.

Frequently asked questions

How many square feet is a 12 by 12 room?

144 square feet, from 12 x 12.

How do I convert square feet to square meters?

Divide by 10.764. A 120 sq ft room is about 11.15 square meters.

Do I include closets in square footage?

It depends on the purpose. For flooring or paint, measure every surface you will actually cover. Real estate listing conventions vary, so check the standard used in your market.

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