Carpet Calculator

The formula

Coverage and yield assumptions

Most residential carpet is made in 12 ft widths; some lines come in 13 ft 6 in or 15 ft. Carpet is priced per square yard (9 sq ft) or per square foot. Pad is sold in rolls and is laid without matching, so pad is estimated from the room area plus waste.

Seams and pile direction

When a room is wider than the roll, the carpet must be seamed. The Carpet and Rug Institute's CRI 105 standard recommends keeping seams out of high-traffic paths and doorways where possible, and running all pieces with the pile in the same direction so color looks uniform. The fill strip beside a full width may be cut from the leftover length if the pile direction can match.

Patterns and stripes

Patterned carpet needs extra length for every run so the pattern lines up at seams, similar to wallpaper. Add the pattern repeat to each run, or ask the dealer to measure. Berbers with visible loops also show seams more and benefit from careful layout.

Stairs and closets

Each standard stair takes a piece roughly 3 ft wide by 18–22 in (tread plus riser, wrapped over the nose). A 13-step staircase typically needs 3–4 sq yd. Closets add small fills that can usually come from offcuts if the pile direction matches.

Choosing pad

• CRI recommends pad no thicker than 7/16 in for most residential cut-pile carpet.
• Berber and low-profile carpets need a thinner, firmer pad, often 3/8 in.
• Higher pad density (lb per cubic foot) lasts longer than extra thickness.

Common mistakes to avoid

• Ordering by room area without accounting for roll width and seams.
• Running pieces with pile in different directions.
• Placing seams in doorways and traffic paths.
• Choosing pad that is too thick for the carpet, which voids many warranties.
• Forgetting stairs and closets when getting quotes.

Waste factor

The default 10% on roll length allows for trimming at walls, squaring the cut ends and small errors. Use 5% for simple rectangles with no seams and 15% for patterned carpet or rooms with angled walls and alcoves.

Imperial and metric

Switch the toggle above the inputs to enter ft ↔ m. The page converts metric entries to imperial before calculating, using NIST factors (1 ft = 0.3048 m, 1 in = 2.54 cm), and shows key results in both systems.

Worked examples

Bedroom 14 × 12 ft on a 12 ft roll

Inputs: room length 14 ft; room width 12 ft; roll width: 12 ft; waste factor 10%.

Result: Order about 20.5 sq yd of carpet.

• Units to buy (rounded up): 21 sq yd
• Room area: 168 sq ft (15.6 m²) = 18.7 sq yd
• Widths (runs) of roll: 1 (0 seams)
• Roll length to cut: 15 linear ft (4.7 m)
• Ordered area: 185 sq ft (17.2 m²)
• Carpet pad: 20.5 sq yd

Family room 20 × 16 ft

Inputs: room length 20 ft; room width 16 ft; roll width: 12 ft; waste factor 10%; cost per unit $32.

Result: Order about 46.9 sq yd of carpet.

• Units to buy (rounded up): 47 sq yd
• Room area: 320 sq ft (29.7 m²) = 35.6 sq yd
• Widths (runs) of roll: 2 (1 seam)
• Roll length to cut: 35 linear ft (10.7 m)
• Ordered area: 422 sq ft (39.2 m²)
• Carpet pad: 39.1 sq yd
• Estimated material cost: $1,504.00

Wide room on a 15 ft roll

Inputs: room length 18 ft; room width 15 ft; roll width: 15 ft; waste factor 5%.

Result: Order about 31.5 sq yd of carpet.

• Units to buy (rounded up): 32 sq yd
• Room area: 270 sq ft (25.1 m²) = 30 sq yd
• Widths (runs) of roll: 1 (0 seams)
• Roll length to cut: 19 linear ft (5.8 m)
• Ordered area: 284 sq ft (26.3 m²)
• Carpet pad: 31.5 sq yd

Quick reference for common sizes

The table repeats the first worked example at smaller and larger sizes, keeping every other setting the same, so you can see how the carpet calculator result scales.

Limitations

The calculator handles one rectangular room at a time. For several connected rooms, a professional measure with a seam diagram usually saves yardage. Stairs are not included.