Carpet Calculator — Square Feet & Square Yards
Measure floor area, convert to square yards, and apply an optional percentage allowance and material price. Then use the worked example below to see why carpet roll purchases can differ from floor area.
Last updated:Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
What This Calculator Measures
This is an area calculator, not a carpet roll optimizer. Enter measured dimensions with the correct units. For a room and an attached alcove, use two non-overlapping rectangles in the L-Shape or Irregular option so the shared space is not counted twice. There are no inputs for roll width, pile direction, seam layout, pattern repeat, or padding.
- Total Area and sq yd: raw floor area before any waste. The displayed square yards exclude the waste allowance.
- With waste factor: floor area × (1 + percentage ÷ 100), displayed separately in square feet. The 10% default is an example, not a carpet specification or guaranteed order quantity.
- Estimated cost: allowance-adjusted square feet × your optional price in USD per sq ft. It does not determine the purchased roll cuts or calculate labor.
Leave the generic “Coverage per box / bundle” field blank for broadloom carpet. It divides area by package coverage; it cannot plan linear roll purchases or reuse offcuts.
Carpet Square Footage to Square Yards
1 sq yd = 9 sq ft. Divide square feet by 9, keeping net floor area, percentage-adjusted area, and purchased carpet area separate. A 15 × 20 ft room has 300 sq ft, so the raw conversion is about 33.33 sq yd. If you choose a 10% allowance, the separate result is 330 sq ft; manually dividing that by 9 gives about 36.67 sq yd. Neither value specifies the roll cuts. Use the square feet to square yards calculator for the conversion alone.
Confirm the seller's price unit rather than assuming all carpet is priced alike. A square yard is area; a linear yard is 3 ft of roll length, whose area depends on the roll width. For an illustrative material quote of $27/sq yd ÷ 9 = $3/sq ft, enter 3 in the price field. The 330 sq ft allowance example would show $990. That is area-based arithmetic, not a supplier roll invoice, installed price, or labor estimate; padding, removal, delivery, taxes, and installation charges need separate quotes.
Worked Cut Plan: A Room and an East Alcove
The main floor is 15 ft east–west × 20 ft north–south = 300 sq ft. An attached east alcove extends 2.5 ft east and runs along the southern 10 ft of the main room's east wall: 2.5 × 10 = 25 sq ft. These rectangles share a boundary, not floor area, giving 325 sq ft total.
Assumptions for Both Complete Alternatives
- Product: hypothetical plain, non-pattern-matched broadloom from compatible stock, with a measured 12 ft usable roll width before the seam preparation below. Billing is 12 ft × each purchased cut length. This is not a universal roll width.
- Direction: all pieces within each complete alternative have the same directed pile arrow: north in A, east in B. Both whole-job directions are permitted only as an assumption for this comparison. No individual piece may be rotated 90 degrees or reversed. An installer or manufacturer may reject either direction because of the product, traffic, or lighting.
- Perimeter allowance: add 3 in to every edge of each rectangle, including each shared joining edge. This produces a main cutting envelope of 15.5 ft east–west × 20.5 ft north–south and an alcove envelope of 3 ft east–west × 10.5 ft north–south.
- Main longitudinal seam: additionally reserve 1.5 in on each of its two meeting edges, a combined 3 in = 0.25 ft loss across the joined widths. Preparation at the alcove's shared boundary is contained within its perimeter allowances, not an additional 0.25 ft deduction there.
- Permitted pieces: main-room breadths run continuously end to end, with no extra transverse patching or strip-nesting seams. The alcove is one piece, and its join to the main room is permitted.
- Supply and cutting: assume sufficient continuous stock, half-foot supplier cut increments, and no knife kerf. These widths, allowances, seam restrictions, and sales terms are scenario assumptions, not CRI rules or a complete installation specification.
How to read dimensions: every cut and offcut below is width across the roll × length along the roll/pile, in feet. In A, across means east–west and along points north. In B, across means north–south and along points east. Changing the whole-job direction changes which room dimension must fit across the roll; it does not allow a single piece's pile to turn away from its neighbors.
| Check | A: pile points north throughout | B: pile points east throughout |
|---|---|---|
| Buy for main room | Two full-width cuts, each 12 × 20.5 | Two full-width cuts, each 12 × 15.5 |
| Main pieces before seam trim | 12 × 20.5 and 3.75 × 20.5 | 12 × 15.5 and 8.75 × 15.5 |
| Joined width after seam trim | 12 + 3.75 − 0.25 = 15.5 | 12 + 8.75 − 0.25 = 20.5 |
| Offcut from second main cut | 8.25 × 20.5 | 3.25 × 15.5 = 50.375 sq ft |
| Alcove cutting envelope | 3 across × 10.5 along | 10.5 across × 3 along = 31.5 sq ft |
| Same-pile offcut fit? | Yes: 3 ≤ 8.25 and 10.5 ≤ 20.5 | No: required width 10.5 > 3.25 |
| Additional purchase for alcove | None: cut 3 × 10.5 from the offcut | One full-width 12 × 3 cut; take a 10.5 × 3 piece |
| Whole-job purchased length | 20.5 + 20.5 = 41 linear ft | 15.5 + 15.5 + 3 = 34 linear ft |
| Whole-job purchased area | 12 × 41 = 492 sq ft (about 54.67 sq yd) | 12 × 34 = 408 sq ft (about 45.33 sq yd) |
Why the Larger-Than-Needed Offcut Still Fails in B
After taking B's 8.75 ft main breadth from the second 12 ft cut, the remaining strip is 12 − 8.75 = 3.25 ft across and 15.5 ft along the east-pointing pile. Its 50.375 sq ft exceeds the alcove envelope's 31.5 sq ft, but area alone does not establish fit. The alcove needs 10.5 ft across and 3 ft along, so its width fails even though its length fits.
A 3 × 10.5 rectangle would fit inside that remnant geometrically. Turning that piece 90 degrees to cover the east alcove, however, would turn its pile away from the main room's east-pointing pile. Reversal is not allowed either. Under these assumptions, B therefore needs the new 12 × 3 = 36 sq ft full-width purchase. Crediting the offcut only by area would incorrectly stop at 12 × 31 = 372 sq ft, understating the whole-job purchase by 36 sq ft.
Whole-job comparison: B still purchases 492 − 408 = 84 sq ft less than A, equivalent to 7 linear ft of this roll, despite buying the alcove piece new. A reuses an offcut without another purchase but uses more carpet overall. Neither purchased quantity equals the 325 sq ft floor.
A flat 325 × 1.10 = 357.5 sq ft allowance is not a cut plan: it is less than either demonstrated continuous-breadth plan. This does not prove that every other seam arrangement needs as much material. If this supplier instead rounds each cut up to whole feet, A becomes 12 × (21 + 21) = 504 sq ft, and B becomes 12 × (16 + 16 + 3) = 420 sq ft. The cutting envelopes stay unchanged; the extra length is allowance or remnant, not more floor.
Pile-Direction Guidance and Limits
The Carpet and Rug Institute's CRI 105 — Standard for Installation of Residential Carpet (2019), section 5.2, page 11 (PDF) states:
“Where two or more pieces of the same broadloom carpet are adjacent, the pile direction is required to be the same unless otherwise specified. Uniform pile direction is not required with dissimilar carpet.”
This example uses adjacent pieces of the same broadloom and assumes no exception to uniform pile direction. The citation supports that conditional direction rule, not the example's 12 ft width, trim dimensions, seam layout, or supplier increments. Neither alternative is a global minimum, a certified installation plan, or a supply recommendation. Replace every assumption with the selected product's requirements and have an installer confirm measurements, seam placement, and acceptable direction before ordering.
Plan Padding Separately
First confirm whether the carpet and installation method require a separate cushion. Its product dimensions, permitted seams, and package sizes need their own takeoff; carpet roll offcuts do not imply an equal padding purchase. Follow the selected carpet and cushion specifications rather than a universal pad type, density, or price. This calculator has no dedicated padding quantity or cost inputs.
Carpet for Stairs: Measure the Surface
Measure the width, tread, and riser of each step instead of using a fixed area per stair. For a rectangular step 3 ft wide, with a 10 in tread and a 7 in riser:
- Basic tread-and-riser area: 3 × ((10 + 7) ÷ 12) = 4.25 sq ft per step.
- For 13 identical steps: 13 × 4.25 = 55.25 sq ft.
This is before nosing, returns, landings, and cutting allowances. Measure those separately, and measure tapered or different-sized steps individually. The installation method, pile direction, and approved cuts determine the roll purchase; neither this surface calculation nor a flat waste percentage supplies a stair cut schedule. Padding also needs its own plan.
Before You Order
- Confirm the product's usable and billed roll widths, stock lengths, pattern repeat if any, and permitted pile direction.
- Ask the installer to approve seam locations, edge preparation, perimeter allowances, and any proposed offcut reuse. Check both directional dimensions, not just area.
- Ask the supplier how each cut is rounded and priced. Separate the carpet purchase from cushion, labor, removal, delivery, and taxes.
Frequently Asked Questions
Is carpet sold by the yard or square yard?
A square yard measures area: 1 sq yd = 9 sq ft. A linear yard measures length and covers an area that depends on roll width. Sellers may quote per square foot, square yard, or linear length; confirm both the price unit and the billing width.
How much carpet do I need for a 10x12 bedroom?
The floor area is 120 sq ft, or about 13.33 sq yd. An illustrative 10% allowance gives 132 sq ft, or about 14.67 sq yd, but neither figure is a roll cut plan. Confirm usable roll width, trimming, pile direction, seams, and supplier cut increments rather than automatically ordering 15 sq yd.
Do I need to add extra for stairs?
Measure each tread and riser. For a step 3 ft wide with a 10 in tread and 7 in riser, 3 × (10 + 7) ÷ 12 = 4.25 sq ft. Thirteen identical steps total 55.25 sq ft before nosing, returns, landings, and cutting allowances. This surface area is not a roll order.
How do I convert square feet to square yards for carpet?
Divide square feet by 9. For example, 300 sq ft ÷ 9 is about 33.33 sq yd. Convert net floor area, allowance-adjusted area, and purchased roll area separately; changing units does not add a cutting allowance.
Does the displayed square-yard value include waste?
No. The calculator's sq yd conversion uses raw floor area before any waste. The separate waste result is in square feet; divide that result by 9 if you want allowance-adjusted square yards. Neither display checks roll cuts or offcut fit.
Should I buy padding separately?
Confirm whether the selected carpet and installation method require separate padding. Measure and plan it using its own product dimensions, seam requirements, and package quantities; do not copy the purchased carpet area. This calculator has no dedicated padding inputs or padding-cost output.
What carpet width should I use?
Use the selected product's confirmed usable width and supplier billing width. The 12 ft roll in the worked example is hypothetical, not a universal standard. A nominal 12 ft roll does not guarantee a seam-free fit in a 12 ft room after trimming and seam preparation.
How do seams affect carpet orders?
Seam preparation reduces usable coverage, and permitted seam positions affect the cuts you can use. Adjacent pieces of the same broadloom must have the same pile direction unless otherwise specified. Ask the installer to approve the layout for the product, traffic, and lighting; a flat waste percentage cannot do that.
What price should I enter?
Enter the optional material price in USD per sq ft. For example, $27 per sq yd ÷ 9 = $3 per sq ft. The calculator multiplies allowance-adjusted area by that rate; the result is not a roll invoice or a labor estimate.