Carpet Calculator: Free Online Carpet Calculator
Use our free carpet calculator to determine exactly how much carpet you need for a room, hallway, or set of stairs. Designed for flooring installers and homeowners, this tool converts your room dimensions into square footage and square yards, including a waste factor, since carpet is sold and priced by the square yard.
How to use this calculator.
- Enter room length and width. Input the dimensions of the room in feet.
- Set your waste factor. The default is 10%; increase it for rooms with angles, alcoves, or patterned carpet requiring seam matching.
- Review your results. The calculator displays room area (square feet) and total carpet needed (square yards) instantly.
- Repeat for each room or stair run. Carpet stairs and closets separately, since their shapes don't fit a simple length-times-width calculation.
- Print or save. Use your browser's print function for a quote-ready material list.
How do you calculate carpet quantity and yardage?
Room area is simply length times width. Carpet needed applies the waste factor to that area first, then converts from square feet to square yards, since carpet is priced and cut by the yard.
Room Area (sq ft) = Length (ft) × Width (ft)
Carpet Needed (sq yd) = Length (ft) × Width (ft) × (1 + Waste Factor ÷ 100) ÷ 9
Where:
- Length and width: The dimensions of the room to be carpeted, in feet.
- Waste factor: The percentage added for seams, pattern matching, and offcuts. 10% is standard for a simple rectangular room.
- ÷ 9: The conversion from square feet to square yards (there are 9 square feet in a square yard), since carpet is sold by the square yard.
Example calculation.
Let's calculate carpet needed for a bedroom.
Scenario: A bedroom measuring 15 ft long and 12 ft wide, with a standard 10% waste factor.
- Calculate room area: 15 ft × 12 ft = 180 sq ft
- Add the waste factor: 180 sq ft × 1.10 = 198 sq ft
- Convert to square yards: 198 sq ft ÷ 9 = 22 sq yd
Result: You need approximately 22 square yards of carpet for this 180 sq ft bedroom, including waste.
Tips from the field.
- Add 10% waste for standard rooms. Increase to 15% for rooms with angles, alcoves, or closets, and 20% for patterned carpet that requires seam matching.
- Carpet comes in 12-ft or 15-ft wide rolls. Your installer will lay out the cuts to minimize seams; unusual room widths can increase waste beyond the standard estimate.
- Measure stairs separately. Each stair's tread and riser adds up differently than open floor area; budget roughly 3.5-4.5 sq ft per stair depending on width.
- Don't forget padding. Carpet padding is typically priced separately per square yard and should be replaced along with new carpet, not reused.
- Order all carpet from the same dye lot. Carpet color can vary slightly between production runs, which is especially noticeable in large, open rooms.
- Factor in closets and connected spaces. A closet opening onto the main room adds its own square footage; measure it separately and add it to the total before ordering, rather than eyeballing an allowance.
Disclaimer: This calculator provides estimates for planning purposes only. Actual carpet requirements vary based on room shape, seam placement, and installer layout decisions. Consult a flooring professional for an exact material order. PavementCalculator.com assumes no liability for material overages or shortages.
Cost, price, and density figures on this page reflect approximate U.S. averages as of August 2026 and vary by region, supplier, and material availability.
Frequently asked questions.
How do I calculate how much carpet I need?
Measure room length × width in feet to get square footage. Add 10-15% for waste, seams, and pattern matching. Divide by 9 to get square yards (carpet is sold by the square yard). For a 12×15 ft room (180 sq ft) + 10% waste = 198 sq ft ÷ 9 = 22 sq yd. For stairs: each stair is roughly 2 sq ft (tread) + 1.5 sq ft (riser) = 3.5 sq ft per stair.
How much carpet do I need for stairs?
Measure each stair's tread (depth) and riser (height), multiply by stair width. A standard stair with 10-inch tread + 7-inch riser × 36-inch width = ~4.25 sq ft per stair. For 13 stairs: 13 × 4.25 = 55 sq ft. Add 10% for pattern matching. Use our calculator: enter room dimensions for the main area and add stair calculations separately.
How much does carpet cost per square foot?
Carpet costs $2-$7 per square foot for materials. Including padding ($0.50-$1/sq ft) and installation ($1-$2/sq ft): $3.50-$10 per sq ft total. For a 180 sq ft room: $630-$1,800 installed. Premium wool carpet costs $8-$15+ per sq ft. Carpet is priced per square yard: divide sq ft by 9 for yard pricing.
What carpet waste factor should I use?
Add 10% waste for standard rectangular rooms. Add 15% for rooms with angles, alcoves, or closets. Add 20% for patterned carpet that requires seam matching. Carpet comes in 12-foot or 15-foot wide rolls: your installer will calculate the exact layout to minimize waste.
How often should carpet be replaced?
Carpet typically lasts 5-15 years depending on quality and traffic. Budget carpet lasts 5-7 years, mid-grade 8-12 years, and premium wool 15+ years. High-traffic areas (hallways, stairs) wear faster. Replace when you see matting, stains that won't clean, odors, or visible wear patterns.