How to Calculate Carpet for Stairs

Updated February 21, 2017

Carpeting your stairs can reduce the noise of footsteps and can add an element of safety and comfort to your stairs. Carpet can also serve to tie together rooms and floors, adding a professional decorator's touch to your home. When calculatang how much carpet you need, measure the treads and the risers. The tread of the stair is the horizontal portion where you place your feet on the stair. The riser is the vertical element of the stairway.

Measure the overall width of the stair treads. Round the measurement up to the nearest foot. For example, if the width measures 34 inches, round it up to 36 inches or 3 feet.

Lay the end of the tape at the base of the riser. Run the tape up the riser and over the top of the tread to the next riser base. This is called the stair-measure. In most cases, the riser is approximately 7 1/2 inches high. Treads usually measure 8 to 10 inches deep. If the measurement is 17 1/2 inches, round the overall stair-measure up to 18 inches.

Multiply the number of stairs times the stair-measure. For example, if the number of stairs is 10, multiply that times 18 inches, to get a total length of 180 inches. Divide 180 inches by 12 inches to find the total length in feet, which is 15 feet.

Calculate the square footage of the stairs. Multiply the width in feet times the total length in feet. For example, 3 feet times 15 feet is equal to 45 square feet.

Find the square yardage of carpet required. Carpet is generally sold by the square yard. There are 9 square feet in every square yard. Divide the overall square footage by 9 square feet. The result is the amount of carpet required for the stairs. In the example, 45 divided by 9 is equal to 5 square yards of carpet.


When ordering the carpet, be sure to indicate the overall width of the stairs so the carpet can be pre-cut to this size.

Things You'll Need

  • Tape measure
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