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Construction & Home
Carpet Calculator — How Many Square Yards of Carpet You Need
How many square yards of carpet for a room, hall or stairs
A carpet calculator turns room measurements into the number the flooring store actually quotes you on: square yards of carpet, plus the square footage behind it. Carpet is the one floor that is still sold by the square yard as often as the square foot, and it comes off a roll that is almost always 12 feet wide. Get the math wrong and you either run short mid-install — leaving a seam in the worst possible spot — or pay for yards of broadloom you'll roll up and throw away.
Everything starts with area in square feet: length × width, with both dimensions in feet. A bedroom that measures 12 ft × 15 ft is 12 × 15 = 180 square feet. Because carpet is priced and ordered by the yard, you convert that to square yards by dividing by 9 (a square yard is 3 ft × 3 ft = 9 sq ft). So 180 ÷ 9 = 20 square yards before any waste.
The two numbers that come out of the area:
- Square feet — useful for comparing against laminate, tile or hardwood, which are priced per square foot.
- Square yards — what carpet rolls, pad and most installers actually quote. sq yd = sq ft ÷ 9.
Then comes the part DIY estimates miss: the roll width. Broadloom carpet comes on a 12-ft-wide roll, so a 13-ft-wide room can't be covered in one piece — you either seam in a strip or buy the full 13-ft width and trim, wasting the offcut. That, plus pattern matching, doorways, closets and stair nosings, is why you add a waste factor. For a simple square or rectangular room, 10% is the standard cushion. For rooms wider than 12 feet, hallways, L-shaped spaces, stairs or a bold repeating pattern, bump it to 15–20%, because the roll width forces more seaming and offcuts.
Work the full example: a 12 × 15 room = 180 sq ft = 20 sq yd. Add 10% waste and you're buying 180 × 1.10 = 198 sq ft = 22 square yards. This calculator lets you add several rooms and totals them, applies your waste factor, converts to square yards, and always rounds up — you can't buy a partial square yard of carpet off the roll. Enter a price per square yard (or per square foot) and it estimates the material cost too. Note this covers the carpet itself; pad (underlayment) is usually ordered to the same square yardage, so the same total works for both.
📖 See also: How to Calculate a Tip (and Split the Bill)
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Room area (sq ft) = length (ft) × width (ft) • Total area = sum of all rooms (sq ft) • With waste: total = area × (1 + waste% ÷ 100) • Square yards = square feet ÷ 9 • Carpet to buy (sq yd) = round up (total sq ft ÷ 9) • Constants: 1 square yard = 9 square feet · standard broadloom roll width = 12 ft • Waste factor: 10% simple rectangular room · 15–20% for rooms over 12 ft wide, halls, stairs or patterned carpet
📰 Formula
• Room area (sq ft) = length (ft) × width (ft) • Total area = sum of all rooms (sq ft) • With waste: total = area × (1 + waste% ÷ 100) • Square yards = square feet ÷ 9 • Carpet to buy (sq yd) = round up (total sq ft ÷ 9) • Constants: 1 square yard = 9 square feet · standard broadloom roll width = 12 ft • Waste factor: 10% simple rectangular room · 15–20% for rooms over 12 ft wide, halls, stairs or patterned carpet
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Dividing square feet by 3 instead of 9 to get square yards — a square yard is 9 sq ft, not 3.
- Ignoring the 12-ft roll width, so a 13-ft-wide room comes up short or needs an unplanned seam.
- Using too small a waste factor on stairs, halls or patterned carpet, then running out.
- Measuring in inches and forgetting to convert to feet before multiplying length × width.
- Rounding square yards down — you buy carpet off a roll, so always round up to the next yard.
💡 Tips
- Carpet is quoted by the square yard; divide your square footage by 9 before you call the store.
- For any room wider than the 12-ft roll, expect a seam and bump waste to 15–20%.
- Order the pad (underlayment) to the same square yardage as the carpet — they match.
- Add closets and doorway thresholds to the room area; installers carpet into them.
- Apply the waste factor before rounding to whole yards so the seam allowance isn't lost.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/carpet-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How do I calculate how much carpet I need?
Multiply each room's length by its width in feet to get square feet, add the rooms together, add a waste factor (10% for a simple room), then divide by 9 to get square yards. A 12 ft by 15 ft room is 180 sq ft, or 20 square yards before waste.
How many square feet are in a square yard of carpet?
A square yard is 3 feet by 3 feet, which is 9 square feet. To convert carpet square footage to square yards, divide by 9. So 270 square feet ÷ 9 = 30 square yards.
How do I convert square feet to square yards for carpet?
Divide the square footage by 9. For example, a 360-square-foot area is 360 ÷ 9 = 40 square yards. Carpet stores quote by the square yard, so this is the number you order.
Why is carpet sold in square yards instead of square feet?
Broadloom carpet comes off a wide roll, and the industry has historically priced it by the square yard. Many quotes, the pad and installation labor are all given per square yard, so converting your square footage to yards lets you compare prices directly.
How much extra carpet should I buy for waste?
Add about 10% for a simple square or rectangular room. For rooms wider than the 12-foot roll, hallways, L-shaped spaces, stairs or a repeating pattern, use 15% to 20% because the roll width and pattern matching create more offcuts and seams.
Why does the 12-foot roll width matter for carpet?
Standard broadloom carpet is made on a 12-foot-wide roll. A room wider than 12 feet can't be covered with a single piece, so you either seam in an extra strip or buy the full width and trim, which adds waste. Plan a higher waste factor for wide rooms.
How do I figure carpet for stairs?
Estimate roughly 1.5 to 2 square feet of carpet per stair tread plus the riser, then add it to your room total and use a 15% to 20% waste factor. Stairs need extra material to wrap the nosing and to run the pile in one direction.
Do I need the same amount of carpet pad as carpet?
Yes. Carpet pad, or underlayment, is ordered to the same square yardage as the carpet that goes over it. The total square yards from this calculator works for both the carpet and the pad.
How do I calculate the cost of carpet?
Multiply the square yards you need (after waste and rounding up) by the price per square yard. If your price is per square foot, multiply the total square feet instead. Remember to budget separately for pad and installation.