Carpet Calculator
Enter your room dimensions and optional closet size to calculate carpet area in square feet and square yards. Estimates rolls needed based on standard 12-foot wide carpet rolls.
What is Carpet?
A carpet calculator estimates the total carpet area needed for a room and determines how many rolls to order. Carpet is sold by the square yard and cut from rolls that are 12 feet wide (the standard width in North America), so the calculation must account for both the room area and the roll layout to minimize seams and waste. The first step is calculating the total floor area in square feet, including any closets or alcoves. The area is then converted to square yards by dividing by 9 (since one square yard equals 9 square feet). Carpet retailers price by the square yard, so this is the number you need for cost estimates. However, the actual amount of carpet purchased is determined by the roll layout, not the raw area. Because carpet rolls are 12 feet wide, the number of rolls (or strips) needed depends on the room width. A room that is 12 feet wide or narrower needs just one roll width. A room between 12 and 24 feet wide needs two roll widths, creating one seam. Each roll is cut to the room length. This roll-based approach often results in purchasing more carpet than the exact room area because you cannot buy partial widths — the excess is trimmed and discarded. Seam placement is critical for both appearance and longevity. Seams should run parallel to the primary light source (usually the main window) and should never be placed in high-traffic paths like doorways or hallways. Professional installers plan the layout to hide seams against walls or under furniture when possible. Patterned carpet requires additional material for pattern matching at seams, typically adding 5-10% to the total. The waste factor accounts for trimming along walls, fitting around doorways and closet openings, and cutting errors. A 10% waste factor is standard for rectangular rooms with simple layouts. Increase to 15% for L-shaped rooms, rooms with many doorways, or patterned carpet that requires matching. Stairways and hallways have higher waste rates due to the many cuts required. Carpet padding (also called underlay or cushion) is required under most carpet types and is sold in the same square yard measurement. Standard residential padding is 7/16-inch thick with a density of 6 to 8 pounds. The padding area matches the carpet area, so the same calculation applies. For cost budgeting, multiply the total square yards by the carpet price per square yard. Include padding ($2 to $4 per square yard) and professional installation ($3 to $6 per square yard, or $1 to $2 per square foot) for the complete project cost.
How to Calculate
- Measure the room length in feet (the longer dimension)
- Measure the room width in feet (the shorter dimension)
- If the room has a closet, measure the closet length and width in feet
- Set the waste factor (10% for simple rectangular rooms, 15% for complex layouts)
- Review the total area in square feet and square yards for pricing
- Check the number of 12-foot wide rolls needed to cover the room width
- For multiple rooms, calculate each room separately and add the totals
Formula
Room Area = Room Length (ft) x Room Width (ft) Closet Area = Closet Length (ft) x Closet Width (ft) Total Area (sq ft) = (Room Area + Closet Area) x (1 + Waste Factor / 100) Total Area (sq yd) = Total Area (sq ft) / 9 Rolls Needed = ceiling(Room Width (ft) / 12) Where 9 is the number of square feet per square yard, 12 is the standard carpet roll width in feet, and each roll is cut to the room length.
Example Calculation
A 15 ft x 12 ft room with no closet and 10% waste: Room Area = 15 x 12 = 180 sq ft Closet Area = 0 x 0 = 0 sq ft Total Area (sq ft) = (180 + 0) x 1.10 = 198 sq ft Total Area (sq yd) = 198 / 9 = 22 sq yd Rolls Needed = ceil(12 / 12) = 1 roll
Frequently Asked Questions
Why is carpet sold by the square yard instead of square foot?
The carpet industry has traditionally used square yards as the standard unit of measure in North America. One square yard equals 9 square feet. Some retailers are shifting to square foot pricing for simplicity, but wholesale and trade pricing is still primarily quoted per square yard. To convert, divide the price per square yard by 9 to get the price per square foot.
What is the standard carpet roll width?
In North America, the standard carpet roll width is 12 feet. Some specialty carpets are available in 13.5-foot and 15-foot widths, and carpet tiles come in 18-inch or 24-inch squares. In Europe, 4-meter (approximately 13-foot) rolls are common. Always confirm the roll width with your retailer before calculating.
How much extra carpet do I need for pattern matching?
Patterned carpet requires extra material to align the pattern at seams. The amount depends on the pattern repeat — the distance before the pattern starts over. Add one pattern repeat length per seam to your order. For a typical 18-inch pattern repeat and a 15-foot seam, add about 1.5 feet per strip, which usually works out to 5-10% additional material.
Should I include the carpet padding in my calculation?
Yes. Carpet padding is required under most broadloom carpet and is measured in the same square yards as the carpet itself. The padding area equals the carpet area, so you can use the same total from this calculator. Standard residential padding is 7/16-inch thick rebond with 6 to 8 pound density. Berber and low-profile carpets require thinner, firmer padding.
How much does carpet installation cost?
Professional carpet installation typically costs $3 to $6 per square yard (about $0.50 to $1.00 per square foot) for labor only, plus $1 to $3 per square yard for removal and disposal of old carpet. Many retailers offer free or discounted installation with carpet purchases. Stairs add $10 to $20 per step due to the additional cutting and fitting required.
Can I install carpet over existing carpet?
Installing new carpet over old carpet is not recommended. The old carpet creates an unstable base that accelerates wear, traps moisture and allergens, and voids most carpet warranties. Always remove old carpet and padding down to the subfloor, then install new padding and carpet. The one exception is commercial-grade glue-down carpet over concrete, where a second layer may be acceptable per manufacturer guidelines.