Buying Rolled Carpet
Wall-to-wall carpeting remains one of the most popular flooring choices for bedrooms, living rooms, and basements due to its warmth, sound-dampening qualities, and comfort. However, unlike square floor tiles or laminate planks, carpet is sold on massive, continuous rolls.
Because carpet comes on fixed-width rolls, calculating how much to buy is not as simple as just finding the square footage of your room. You must calculate how many "drops" (lengths cut from the roll) you need to cover the width of the room, and how much waste will be generated by the seams.
Understanding Carpet Roll Widths
In the United States, broadloom carpet is almost universally manufactured and sold in 12-foot wide rolls (though 15-foot rolls are available for premium lines).
When you purchase carpet, you are essentially buying it by the Linear Foot off that 12-foot roll. Because of this fixed dimension, rooms that are not perfectly divisible by 12 generate significant waste.
How to Calculate Carpet Needs
To determine how many linear feet you need to order off the roll, you must orient the carpet drops in a way that minimizes seams and waste.
The Calculation Logic
- Decide which direction you are running the carpet. Usually, you run the carpet parallel to the longest wall to minimize the number of seams.
- Divide the Room Width by the Carpet Roll Width (usually 12) to see how many "drops" (strips) of carpet you need. Round up to the nearest whole number.
- Multiply the number of drops by the Room Length to get the total Linear Feet required.
(Note: Carpet is directional. The fibers lay in a specific direction. If you use two drops of carpet side-by-side, they must face the exact same direction, or the seam will be glaringly obvious because the light will hit the fibers differently).
Example Calculation
You are carpeting a master bedroom that is 16 feet wide and 20 feet long. You are buying from a standard 12-foot wide roll.
- Run the drops along the 20-foot length.
- Determine drops needed to cover the 16-foot width:
16 ÷ 12 = 1.33 drops. Round up to 2 drops. - Determine total linear feet:
2 drops × 20 feet = 40 Linear Feet.
You must order 40 linear feet from the 12-foot roll (which equals 480 square feet of carpet).
Notice the massive waste! Your room is only 320 square feet (16x20), but because you had to cut a full 12-foot drop to fill a 4-foot gap, you had to buy 480 square feet of carpet. This is the reality of broadloom carpet installation.
The Importance of Seam Placement
If your room requires more than one drop of carpet, you will have a seam where the two pieces are hot-melted together. Professional installers spend a lot of time planning seam placement.
You should never place a seam directly in the center of a doorway, in a high-traffic hallway, or running perpendicular to a major light source (like a large sliding glass door), as the light will highlight the seam. Sometimes, it is worth buying extra carpet just to shift the seam to a hidden corner under a bed.