Everyday
Carpet Calculator
Size carpet for rooms and staircases: strip layout, 12 ft vs 15 ft roll comparison, and cost per square yard.
How it works
Behind the numbers
Carpet comes in 12 ft and 15 ft wide rolls, and strips run across the room to keep seams few. For each room the calculator tries strips across both sides and keeps the lower-area layout, the same choice an installer makes on site. Waste is the difference between the roll area used and the room area, shown separately for each roll width so the recommendation is visible rather than hidden.
Stairs are measured differently: each step needs its tread depth plus riser height plus one inch to wrap the nose. Multiply by the step count and the stair width to get the area, then convert to square yards. A typical 13-step staircase with 11-inch treads and 7-inch risers needs about 7 square yards before waste.
Carpet is priced per square yard, which is 9 square feet. The buy quantity rounds the needed square yards up and adds your waste allowance, 10% by default and more for patterned carpet, then multiplies by your price per square yard. Room and stair modes share the waste and price fields.
FAQ
Questions, answered
How much carpet do I need for a 12x15 room?
A 12 by 15 ft room is 180 sq ft, or 20 square yards before waste. With a 12 ft roll, one 15 ft strip covers it with no cutting waste; with a 15 ft roll, one 12 ft strip does the same. Add 10% waste and plan on buying 22 square yards.
Should I buy a 12 ft or 15 ft carpet roll?
It depends on the room shape. The calculator prices both widths for your rooms and recommends the lower-waste one. As a rule, rooms under 12 ft wide usually waste less on a 12 ft roll, while rooms between 12 and 15 ft wide fit a 15 ft roll with one strip.
How do you calculate carpet for stairs?
Add the tread depth and riser height plus one inch for the nose wrap, multiply by the number of steps and the stair width. A 13-step staircase at 3 ft wide with 11-inch treads and 7-inch risers needs about 61.75 sq ft, or 7 square yards before waste.
What is a square yard of carpet?
One square yard equals 9 square feet. Carpet is priced and sold by the square yard, so a 180 sq ft room needs 20 square yards before the waste allowance. The calculator converts and rounds up to whole yards for ordering.