Carpet Calculator
Work out how much carpet to order - enter the room size and the roll width to get the square yards off the bolt, the padding, tack strip and seam tape, plus a material cost estimate.
United States — national average · 2026 prices
Material only unless stated as installed. Excludes tax, permits and local labour. Verify with local suppliers — see how we calculate.
How this calculator works
Every figure above comes from the formula below, applied to the assumptions listed. Nothing is looked up from a hidden table — you can reproduce the result by hand.
Formula
strips = ⌈room width ÷ roll width⌉ · linear ft = strips × run length
the calculator tries both orientations and keeps the one with fewer linear feet
order linear ft = (room + stairs × 1.5) × (1 + cut waste ÷ 100)
square yards = order linear ft × roll width ÷ 9
Assumptions & limits
- Carpet is roll goods in fixed widths — 12 ft is the US standard, 15 ft and 13 ft 2 in (4 m) also exist. Strips are never joined across the width, so the width always rounds UP to a whole strip.
- All strips must run the same pile direction. That is why the calculator cannot simply divide floor area by nine, and why a 13 ft wide room off a 12 ft roll carries about 20% roll waste.
- Cut waste defaults to 5% on top of the layout, covering trimming and the extra few inches installers leave at each wall.
- A stair step is treated as 1.5 ft of run (about a 10 in tread plus an 8 in riser) at 3 ft wide. Wider stairs, winders and wrapped bullnose steps take more.
- Padding is sized at floor area plus 5% — it is butted and taped, not laid in strips — and comes in 6 ft wide rolls of about 270 sq ft.
- Tack strip is the room perimeter minus 3 ft per doorway, sold in 4 ft lengths. Seam tape is counted only where the layout actually produces a seam.
- Carpet price defaults to $27 per square yard (about $3/sq ft), mid-grade. Real material spans roughly $1.50/sq ft builder-grade to over $8/sq ft for wool. Padding defaults to $0.60 per sq ft. Labor is excluded here — use the carpet installation cost calculator for an installed figure.
Worked example
A 20 × 20 ft room off a 12 ft roll, one doorway, 5% cut waste, carpet at $27/sq yd and padding at $0.60/sq ft
- Strips = ⌈20 ÷ 12⌉ = 2 · linear ft = 2 × 20 = 40 ft
- Order = 40 × 1.05 = 42 ft off the roll = 42 × 12 = 504 sq ft
- Square yards = 504 ÷ 9 = 56.0 (floor alone is 44.4) → 20.6% roll waste
- Carpet 56.0 × $27 = $1,512 · padding 420 sq ft × $0.60 = $252 · tack strip, seam tape and transitions ≈ $73
Result:About 56 square yards to order and one seam — roughly $1,650 to $2,110 in carpet, padding and supplies.
Built and maintained by Christoph Ballmer, Honeygoat GmbH
Method and constants last checked against the calculator code on September 1, 2026. Independent trade review is not yet in place for this calculator — see how we handle review.
Read the site-wide calculation methodology · estimate vs. quote and safety limits
Why carpet is not just floor area divided by nine
Every other flooring material on this site is sold by the piece or the box, so the arithmetic is coverage divided by unit size. Carpet is different: it comes off a roll of fixed width, almost always 12 feet in the United States, and it cannot be joined across that width without a visible seam. That single fact is what makes a naive answer wrong.
A 10 × 10 ft room is 100 square feet — 11.1 square yards of floor. But the narrowest piece that covers it in one go is 10 feet of a 12-foot roll: 120 square feet, or 13.3 square yards. You buy the full width of the bolt whether the room uses it or not, and the leftover 2 feet runs the whole length of the room. That is not waste you can avoid by measuring more carefully; it is a property of the product.
strips = ⌈room width ÷ roll width⌉ · linear ft = strips × run length · sq yd = linear ft × roll width ÷ 9
Which way should the carpet run?
When a room is wider than the roll, you need two or more strips and at least one seam — and then the orientation matters. Laying strips the long way and the short way give different linear footages, and the calculator computes both and keeps the cheaper one. There is a constraint you cannot design around, though: all strips must run the same pile direction. Carpet pile lies one way, and two pieces turned against each other read as two different colours under the same light. Installers will not rotate a strip to save material, and neither should the estimate.
Roll width against room width
Waste depends on both room dimensions, not the width alone, so the table below fixes the room at 20 feet long and varies the width. Percentages are the layout waste before the cut allowance the calculator adds on top.
| Room (20 ft long) | Off a 12 ft roll | Off a 15 ft roll | Seam |
|---|---|---|---|
| 12 ft wide | 1 strip · 0% waste | 1 strip · 20% waste | None either way |
| 13 ft wide | 2 strips · 16.7% | 1 strip · 13.3% | 12 ft: yes · 15 ft: no |
| 15 ft wide | 2 strips · 16.7% | 1 strip · 0% | 12 ft: yes · 15 ft: no |
| 20 ft wide | 2 strips · 16.7% | 2 strips · 33.3% | Yes either way |
| 24 ft wide | 2 strips · 0% | 2 strips · 20% | Yes either way |
Two things fall out of that table. First, a wider roll is not automatically the efficient one — a 20-foot-wide room wastes twice as much off a 15-foot roll as off a 12-foot roll, because the second strip contributes only 5 feet of the width it charges for. Second, the 13-foot-wide room is the case worth planning around: on the standard 12-foot roll it takes a seam down the middle, while a 15-foot roll covers it in one piece for slightly less material. The seam is the real cost there, not the yardage. Ask the retailer which widths that specific style is made in before you settle on a layout — many styles are 12 foot only, and that answer decides it.
What else goes in the order
Carpet is the headline number, but four other items go on the ticket, and the calculator sizes each of them:
- Padding (cushion). Floor area plus about 5%, because it is butted and taped rather than laid in strips. Standard residential cushion is 6–8 lb density at 7/16 in, sold in 6 ft wide rolls of roughly 270 square feet. Reusing old padding is a false economy — it is permanently compressed, and most carpet warranties require new cushion.
- Tack strip. The room perimeter minus about 3 feet per doorway, in 4-foot lengths. It is what holds a stretch-in carpet under tension; if the existing strip is sound and not rusted, it can often stay.
- Seam tape. Only where the layout actually produces a seam. The calculator counts the seams it created rather than assuming a fixed number.
- Transition strips. One per doorway, to meet tile, wood or the next room's carpet cleanly.
Stairs
Stairs are estimated separately because they consume carpet by the step, not by the square foot of plan. A standard step takes roughly 1.5 feet of run — about a 10-inch tread plus an 8-inch riser — at about 3 feet wide, and the calculator adds that to the linear footage off the roll. Winder steps, wrapped bullnose ends and stairs wider than 3 feet all take more, so treat the stair figure as a floor rather than a ceiling. If the stairs are the whole job, have the installer measure them: a mis-cut stair piece cannot be salvaged.
Common mistakes
- Ordering by floor area. The most expensive mistake on this page. Floor area understates roll goods by anywhere from 3% to over 30% depending on the room width.
- Forgetting the closets and the doorway strips. Carpet runs into closets and a few inches past each doorway. Measure to the far side of the threshold.
- Adding rooms together. Three 12 × 10 rooms are not one 360 sq ft area — each is cut from the roll separately. Run them through the calculator one at a time.
- Assuming a remnant will match. Dye lots vary between rolls. If a repair piece matters to you, buy the offcut with the order and keep it.
Related planning
Once you know the quantity, the carpet installation cost calculator turns it into an installed price with labor, take-up and stairs. If you are still comparing floor types, the flooring calculator sizes laminate, vinyl and hardwood by the box, and the tile calculator handles tile. Painting first is the right order of operations — the paint calculator covers that.
Figures are planning estimates for material quantities and 2026 US national price ranges. Roll widths, dye lots and actual coverage vary by style, so confirm the available widths and the final measurement with your retailer or installer before ordering.
Frequently asked questions
How do I calculate how much carpet I need?
Not by dividing the floor area by nine. Carpet is roll goods, sold in fixed widths - normally 12 ft, sometimes 15 ft - and every strip has to run the same pile direction. So the real question is how many linear feet come off the bolt: divide the room width by the roll width and round UP to whole strips, multiply by the run length, then add about 5% for cuts. The calculator above tries both orientations and keeps the cheaper one.
How many yards of carpet do I need for a 10x10 room?
A 10 x 10 room is 100 sq ft, which is 11.1 square yards of floor - but you cannot buy 11.1. Off a 12 ft roll you take one strip 10 ft long: 120 sq ft, or 13.3 square yards, and about 14 square yards once a 5% cut allowance is added. The 2.9 square yards of difference is the strip of roll left over beside the room, and you pay for it either way.
How much to carpet a 20x20 room?
A 20 x 20 room is 400 sq ft. Off a 12 ft roll it takes two strips 20 ft long - 480 sq ft, about 56 square yards with the cut allowance, so roughly 20% roll waste and one seam down the room. At $27 per square yard for mid-grade carpet that is about $1,500 in carpet, plus roughly $250 of padding and $70 of tack strip, seam tape and transitions. Installed, the same room typically lands near $2,000 to $2,900.
How much would 1,000 sq ft of carpet cost?
For material alone, 1,000 sq ft of floor needs roughly 120 to 130 square yards of roll goods once layout waste is counted - about $1,600 to $3,500 in carpet at builder-grade to mid-grade prices, plus $300 to $600 of padding. Installed with take-up and disposal, 1,000 sq ft commonly runs $3,500 to $11,000 depending on the grade. Enter your rooms above rather than the total: waste depends on the shape, not the sum.
Does carpet come in 12 ft or 15 ft rolls?
Both, and the choice changes the waste. 12 ft is the dominant US width and what most stock rolls carry; 15 ft is common in commercial goods and useful for rooms 13 to 15 ft wide, where a 12 ft roll would force a second strip and a seam. A 13 ft wide room takes 20% waste off a 12 ft roll and almost none off a 15 ft roll. Ask what widths your carpet is actually available in before you plan the layout.
Do I need new carpet padding too?
Almost always, yes. Padding compresses permanently, and reusing flattened cushion under new carpet is the fastest way to void the carpet warranty and lose the feel you paid for. Standard residential cushion is 6 to 8 lb density at 7/16 in thickness; it comes in 6 ft wide rolls of about 270 sq ft. The calculator sizes it at floor area plus 5%, since padding is butted and taped rather than laid in strips.