Carpet Calculator - Square Yards & Cost Estimator

How to use this tool

1. Choose Imperial or Metric, then enter the width and length of each rectangular room.
2. Choose a carpet roll width and set a waste percentage; add a price per square yard if you want a material estimate.
3. Review the separate room strip layouts, total seams, ordered length and area, and estimated material cost.

How to measure for carpet

Enter each rectangular room separately. The calculator adds the room areas for a net floor total; in Imperial mode, multiply each room’s length by its width in feet and divide the result by 9 to convert square feet to square yards. Metric dimensions are converted to feet for the roll layout while the net area is also shown in square meters. Splitting an L-shaped room into rectangles is a practical way to estimate it, as long as each part is entered as its own room.

Square yards = (Length ft × Width ft) ÷ 9

Roll width, strips, and order length

Carpet is commonly sold in wide rolls, so floor area alone does not show how many cuts are needed. Choose a 12-foot or 15-foot roll in Imperial mode, or a 4-meter or 5-meter roll in Metric mode. For every room, the calculator checks both orientations: it divides each possible cross-room dimension by the roll width, rounds up to a whole number of strips, then multiplies the strip count by the run length. It selects the orientation with fewer linear feet; when the lengths tie, it prefers fewer seams. Separate rooms are laid out independently and their cut lengths are added together, so rooms are never combined into a single rectangle.

For example, a 12-by-15-foot room on a 12-foot roll needs one 15-foot strip. With a 10% waste allowance, the order estimate is 16.5 linear feet, or 198 square feet (22 square yards) at that roll width. A separate area-only tile still shows the measured floor area plus its percentage allowance for comparison. The roll estimate applies waste once to its calculated linear feet, then multiplies that adjusted length by roll width to get ordered square feet and square yards. If you enter a price per square yard, estimated material cost uses those geometry-based ordered square yards.

Waste factor and limitations

A 10% allowance is a common starting point; patterns, diagonal installations, room complexity, and installer requirements may call for more. Strip counts and seams are estimates based on rectangular dimensions and the selected roll width. Pattern repeats and required carpet-pile direction can affect the actual cut plan, so confirm the layout and final order with your installer before purchasing.

Reasons the amount of extra carpet can vary include:

• Pattern matching: patterned carpets may need extra length to align the repeat at seams.
• Irregular rooms: L-shaped or angled rooms can produce offcuts that cannot be reused efficiently.
• Roll width: room dimensions that do not divide evenly into the selected roll width may leave unusable offcuts.

Don’t forget carpet padding

Carpet padding (underlay) adds cushioning, insulation, and extends carpet life. Order padding at the same square yardage as your carpet. Standard padding is 7/16” thick at 6–8 lb density for most residential use. Higher density (8+ lb) is better for heavy-traffic areas.

Measuring irregular rooms

For L-shaped rooms, break the space into two rectangles, calculate each separately, and sum the areas. For rooms with alcoves or bump-outs, measure the largest bounding rectangle and then subtract any areas that will not be carpeted (e.g., a closet with a different floor covering). Always round up when in doubt - it is much harder to add carpet after installation than to return a small unused remnant.

Stair carpet calculation

This calculator estimates flat rectangular rooms only; it does not take stair measurements or calculate stair carpet. As a separate reference, a basic stair runner estimate uses stair width × (tread depth + riser height) × number of steps, with extra material for tucking and waste. Stair shapes and installation styles vary, so use the Stair Calculator for a dedicated stair estimate and confirm measurements with an installer.

Carpet types