Reviewed October 2026 · Prices checked October 2026 · How we calculate

Carpet Calculator: How Much Carpet Do I Need?

Enter the room's length and width. You get the square yards of carpet to buy off the roll, laid out to need the least, plus pad and tack strip, and what it costs at your store's price.

How it works

The formula

strips = (room width + 6 in) ÷ roll width, rounded up
strip length = room length + 6 in for trimming
carpet (sq ft) = strips × roll width × strip length; try both directions, keep the smaller
sq yd = sq ft ÷ 9, rounded up

Assumptions

Carpet comes off a roll 12 or 15 ft wide, and you buy whole widths: a 13 ft wide room on a 12 ft roll needs two strips, with an offcut. Installers can sometimes use offcuts as fill pieces; we don't count on it, so the total errs on the safe side.
Every wall gets 3 in extra for trimming, as the carpet industry's installation standard (CRI 105) asks: at both ends of each strip, and at both side walls. So a room 12 ft wide needs 12 ft 6 in of carpet across, more than a 12 ft roll: a seam, or a 15 ft roll.
Pad covers the floor only, with no waste. Tack strip goes around the whole room in 4 ft pieces; take off any doorways and hard-floor edges.
Typical prices: carpet $30–$50 per sq yd, pad $2.25–$10 per sq yd (checked Oct 2026). Installation is extra.
Closets, bump-outs and stairs need their own pieces. Measure them as separate rooms and add them up.

Worked example

A 15 × 20 ft family room on a 12 ft roll

Along the 20 ft length: 15.5 ft across needs 2 strips × 12 × 20.5 ft = 492 sq ft
Along the 15 ft width: 20.5 ft across needs 2 strips × 12 × 15.5 ft = 372 sq ft, less carpet
372 ÷ 9 = 41.33, so buy 42 sq yd, with one seam
Pad: 300 ÷ 9 = 33.3, so 34 sq yd

Carpet for common room sizes

Square yards of carpet for common rooms on 12 and 15 ft rolls, and pad
Room	Floor sq ft	12 ft roll	15 ft roll	Pad sq yd
10 × 10 ft	100	14 sq yd	18 sq yd	12
11 × 14 ft	154	20 sq yd	20 sq yd	18
12 × 12 ft	144	34 sq yd, 1 seam	21 sq yd	16
14 × 16 ft	224	39 sq yd, 1 seam	28 sq yd	25
15 × 20 ft	300	42 sq yd, 1 seam	52 sq yd, 1 seam	34
20 × 24 ft	480	66 sq yd, 1 seam	69 sq yd, 1 seam	54

Questions people ask

How much carpet do I need for a 12 × 12 room?

With the 3 in trim allowance at every wall, the room needs 12.5 × 12.5 ft of carpet. On a 15 ft roll that's one piece, 188 sq ft or 21 sq yd, with no seam. On a 12 ft roll it takes two strips and a seam, 34 sq yd, unless the installer can fit the extra from an offcut. Pad: 144 sq ft, or 16 sq yd.

Why do I need more carpet than my floor area?

Carpet comes in fixed roll widths, so you pay for whole widths, plus 3 in at every wall to trim. A 12 ft wide room on a 12 ft roll needs a second strip for the last 6 in. Choosing the strip direction well, or a 15 ft roll, keeps the extra down.

How do I convert square feet to square yards?

Divide by 9, since a square yard is 3 × 3 ft. 200 sq ft is 22.2 sq yd. Carpet is often priced per square yard; divide a per-yard price by 9 for the price per square foot.

How much does carpet cost?

About $30 to $50 per sq yd for mid-range carpet, and $2.25 to $10 per sq yd for pad (checked Oct 2026). Installation is usually extra and often quoted per square yard too. Type your store's prices into the list for an exact total.

Which way should carpet seams run?

Ideally toward the main light source, like a large window, and out of busy walkways, where they show least. The cheapest layout isn't always the best-looking one; ask the installer before you order.