Calculating the amount of carpet needed for stairs is an important step when ordering your carpet. You don't want to get to the last few stairs and realise you won't have enough material. There are many benefits to using carpeting on stairs. It acts as a noise buffer on squeaky old stairs, it adds a degree of insulation in colder climates and it hides imperfections in the stairs' quality. To reap these benefits you must properly calculate how much carpeting you'll need.
With an expandable tape measure, determine the width of the staircase. When calculating for the purpose of buying carpeting, always round up to the closest foot.
Measure the rise and depth of one stair. The rise is the height of the "kicker" portion of the stair. The depth is the distance from the stair's edge until it meets the riser, or kicker. Take the tape measure and lock the edge at the bottom of a stair. Move the tape up the riser and across the depth of the stair until you reach the next riser. Write this number down.
Determine the number of stairs you want to carpet. Multiply the number of stairs by the measurements of the rise and depth. As always, round up to the nearest foot.
Multiply the number you got for the width of the staircase by the number you came up with in the previous step. This gives you the square footage of the entire staircase. Buy this amount of carpet.
Carpenter's rule applies: Measure twice, cut once.
If your stairs are exceptionally deep or have a large lip, you may need someone to assist when holding the measuring tape in place.