From staircase measurements to a continuous flight piece
Begin at the intended upper termination and follow the exact route the carpet will take to the lower termination. A stair has a horizontal tread and a vertical riser, but the number of each that receives carpet can differ. The upper floor may replace the last tread, or the runner may finish below a top riser. Count the covered surfaces on the actual staircase.
Sisal Rugs Direct describes a useful check: secure a string along the intended installation route, including the nose treatment, and measure the resulting path. Its mathematical method also counts risers and tread depths independently. A straight-line rise-and-run measurement can miss the material used by a wrapped nose. Here, extra nose path is an entered measurement, not a guessed multiplier.
Flight path = tread count × (tread path + extra nose path)
+ riser count × riser path
For uniform straight flights, that formula is exact for the entered measurements. Two flights can have different tread depths, riser heights and counts. If individual steps within one flight vary materially, measure the full path and have the supplier check the cut; this interface does not accept a separate dimension for every step. Winder treads and spiral stairs require shaped pieces and are outside the rectangular model.
End allowances are not pattern allowances
Top and bottom allowances are added to every continuous piece, including the landing. The example uses 3 inches at each end, totaling the six extra inches suggested by the measuring guide. This is an editable example allowance; your supplier may specify another amount for trimming, binding or termination. A landing piece with two cut ends may need a different treatment in the real installation.
After those allowances, each piece is rounded up to the entered lengthwise repeat. A 223.5-inch flight with a 24-inch repeat becomes a 240-inch cut. The extra 16.5 inches belongs to pattern rounding. It is different from the end allowances and from the unused roll strip beside the runner, and the result keeps those quantities separate.
Why square feet do not specify a broadloom order
Carpet comes from a roll of a particular width. A long narrow flight and a short wider landing can often sit beside one another on the roll. Their net area is not the same as the full-width area purchased. Conversely, two narrow pieces may need separate lengths if their combined widths exceed the roll.
The layout uses a shelf method. Longest pieces are placed first; each later piece goes alongside an existing shelf when enough roll width remains, otherwise a new shelf starts after it. All pieces point in the same roll direction and no piece is rotated merely to save material. Every flight remains continuous, with no seam inserted halfway down a staircase.
This produces a physically feasible rectangular arrangement under the stated assumptions. It is not a proof of the shortest possible purchase. An experienced cutter may use the empty space beside short pieces more effectively, or choose different seam locations on a landing. The diagram and CSV make the plan inspectable instead of presenting an unexplained percentage as a cutting result.
The default staircase, reconciled by hand
Twelve 10-inch treads contribute 120 inches. Thirteen 7.5-inch risers contribute 97.5 inches. With no extra nose path, the flight covers 217.5 inches; adding the two end allowances gives a 223.5-inch cut. The 36 by 42 inch landing becomes 36 by 48 inches after those same allowances.
On a 144-inch roll, the 27-inch flight and 36-inch landing occupy 63 inches of width together. They share one 223.5-inch shelf. The seller’s 12-inch length increment rounds the order to 228 inches, or 19 linear feet. Full-width purchased area is therefore 228 square feet. Net coverage is about 51.28 square feet; the difference is unassigned or allowance material, not additional stair coverage.
Runner orders and broadloom orders use different ledgers
If the supplier sells a finished runner in the exact narrow width, take the flight dimensions from the continuous-piece table. The broadloom headline assumes you pay for the complete roll width. Applying that full-width area to a narrow finished runner can overstate the material purchase substantially.
A finished runner can also have binding restrictions, an available maximum length, or a different treatment for landing pieces. Confirm which edges arrive finished and which may be trimmed. The calculator does not calculate binding length or choose an installation method; it hands you the rectangle dimensions and ordering assumptions that the supplier needs to confirm.
Check the landing before committing a patterned order
A straight repeat along a roll does not guarantee matching across a 90-degree turn. The orientation of the motif on the landing, the pile direction on the next flight and the seam location may impose constraints beyond simple cut length. This plan deliberately keeps all pieces in one pile direction and labels its pattern calculation as repeat rounding only.
Measure the landing cut rectangle in the orientation it must occupy on the roll. If it is wider than the roll, the tool raises an error rather than drawing an impossible rectangle or hiding a seam. Do not reduce the entered width just to clear that error. A wider product, an approved seam plan or a separately supplied landing piece is needed.
For adjacent rectangular rooms, the rectangular-room carpet tool handles room drops and fill-strip seams. Those room seams should not be carried onto a flight by assuming all carpet is interchangeable square footage.
Stair carpet and runner questions
How do you calculate how much carpet you need for stairs?
Count covered treads and covered risers separately. Multiply each count by its measured path, add any nose-wrap length not already included, then add the two end allowances. That gives a continuous flight piece. For broadloom, place that piece and any landing across the actual roll width before rounding the order length; net stair area alone does not specify how much roll to buy.
How long should carpet be for 13 stairs?
“13 stairs” can mean 13 risers but only 12 covered treads. In this example, 12 treads at 10 inches and 13 risers at 7.5 inches make 217.5 inches of measured path. Two 3-inch end allowances bring the flight cut to 223.5 inches, or 18 feet 7.5 inches, before any pattern rounding. Count what will actually receive carpet rather than copying that example for a different staircase.
How much carpet is needed for 14 stairs?
If you mean 14 covered treads and 14 covered risers, each 10 and 7.5 inches respectively, the measured path is 245 inches. With 3 inches at each end, the piece is 251 inches before a repeat. If the upper floor replaces the last tread, the count changes. Enter the two actual counts and measure any landing separately.
How long does a runner need to be for 15 stairs?
For 15 treads at 10 inches and 15 risers at 7.5 inches, the path is 262.5 inches, or 21 feet 10.5 inches. Adding a 3-inch allowance at each end gives a 268.5-inch cut. A 24-inch repeat would raise that piece to 288 inches. These are conditional examples; a waterfall path, a wrapped nose or a different top termination can change the measurements.
Can I include a landing in the stair carpet calculation?
Yes. Turn on the rectangular landing and enter its cut width and path length. It becomes a separate piece with its own end allowances and repeat rounding. The layout keeps it in the same roll direction as the flights. A turning pattern, a continuous wrap through a corner or an irregular landing still needs an installer’s seam and pattern plan.
How do I calculate the carpet area needed for my stairs?
Multiply runner width by each measured flight path, add the landing width times its measured length, and divide square inches by 144 for square feet. The result is net coverage. Purchased area is the entire roll width times the rounded order length, including unused strips, end allowances and repeat surplus. This calculator displays both quantities so they cannot be mistaken for one another.
Can I calculate stair carpet in meters or square meters?
Switch to metric to convert all length fields to millimeters. The result shows dimensions in metric and areas in square meters, while the headline also states the broadloom order in linear feet for US ordering. Explicit units such as 4 m are accepted in a length field. Counts remain whole treads and risers; they are never converted.
How much does it cost to carpet 14 stairs?
A reliable quote needs the carpet product, roll or runner sale format, cut schedule, binding, underlay, removal and installation scope. This tool supplies quantities rather than an unsupported installed-price average. A broadloom quote can price the full-width ordered area; a finished runner seller may instead price a narrow width by the linear foot. Ask which basis applies before multiplying a rate.
Does this work as a stair runner calculator?
It calculates each runner’s cut width and length, but the final order assumes those pieces are cut from full-width broadloom. If you are buying a finished narrow runner, use each continuous-piece row and the seller’s ordering rule, not the broadloom headline. Do not add all piece lengths blindly if the supplier offers pre-cut landing pieces or different width products.
Does the 7–11 rule tell me the carpet length?
No. A rise-and-run rule concerns stair geometry, while carpet follows the surfaces and installation path already present. Use measured dimensions and covered counts here. This calculator does not size stringers or determine whether the staircase complies with a building code. A wrapped nose also needs a measured path rather than an assumed extra amount based on a stair-design rule.
Before the cutting schedule becomes an order
- Verify the roll’s sale width, usable width and order increment with the supplier; the filled dimensions are examples.
- The model accepts two uniform straight flights and one rectangular landing. No winders, fans, spiral treads or shaped seams.
- Repeat rounding is lengthwise only. It does not check across-roll repeats, motif centering, pattern distortion or matching through turns.
- No seam allowance, binding allowance or installation charge is invented. Enter the extra length your product and installation require.
- Underlay, grippers, adhesives and fastening details need their own specification.