Stair Carpet Calculator
Enter a flight's total rise and tread run, or type the number of stairs, to get the length of carpet for the treads and risers, the square yards at your stair width and the roll to buy, rounded up once.
A ready-made setup of the Carpet Calculator.
Estimates for planning, not professional advice. Read the full notice.
Example: a straight flight
22 carpet, by the linear foot
- Risers 14 risers
- Treads 13 treads
- Riser height 7.714 in
- Length covered 19 ft 10 in
- Square yards at the stair width 7.27 sq yd
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Carpet, by the linear foot | carpet, by the linear foot | 22 |
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Worked example: a straight flight
Show the working
- Treads: the tread run times the treads 10 in × 13 treads = 10 ft 10 in
- Risers: the riser height times the risers 7.714 in × 14 risers = 9 ft
- Add the waste allowance, once 19 ft 10 in × 1.1 = 21 ft 9 13/16 in
- Roll length: the strips across the stair width, times that length 1 strip × 21 ft 9 13/16 in = 21 ft 9 13/16 in
- Round up once, to whole feet of roll 21 ft 9 13/16 in = 22 linear ft of carpet
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Waste allowance | 10% | |
| Default A typical allowance, added once to the length covered. Change it for your job. | ||
| Stair width | No default | |
| Default The width of the carpet on the stair. Check your label or supplier. | ||
| Nosing wrap per tread | 0 in | |
| Default Extra carpet turned over each nosing, our assumption of none. Check your label or supplier. | ||
| Roll width | No default | |
| Default Choose the width of your roll from the list; the three widths are the Carpet and Rug Institute's. | ||
| Largest riser you will allow | 7.75 in[1] | |
| Default Prefilled with the 2021 IRC maximum riser height; type a smaller number for more, lower risers. | ||
| Tread run | No default | |
| Default The depth of a tread from nosing to nosing. Check your label or supplier. | ||
| Top mount | No default | |
| Default Standard: the floor above is the top tread. Flush: the top tread is on the stringer. | ||
Feet and inches, like 12' 6"
What one step takes
The working for the example flight: a tread, a riser, one step and the whole flight, each from the stair engine
| Part | Length |
|---|---|
| Tread run | 10 in |
| Riser height | 7.714 in |
| One step | 17.714 in |
| Treads and risers together | 19 ft 10 in |
| With the waste allowance | 21 ft 9 13/16 in |
One step is its tread run plus its riser height, with any nosing wrap you add. The flight is its treads and risers added, then the waste allowance once.
Carpet for a number of stairs
Length covered and roll length for flights of different numbers of stairs at the example riser and tread, each stair a tread and a riser
| Stairs | Length covered | Roll length with waste | Square yards |
|---|---|---|---|
| 10 stairs | 14 ft 9 1/8 in | 16 ft 2 7/8 in | 5.41 |
| 12 stairs | 17 ft 8 9/16 in | 19 ft 5 13/16 in | 6.5 |
| 13 stairs | 19 ft 2 5/16 in | 21 ft 1 5/16 in | 7.04 |
| 14 stairs | 20 ft 8 in | 22 ft 8 13/16 in | 7.58 |
| 15 stairs | 22 ft 1 11/16 in | 24 ft 4 5/16 in | 8.12 |
Each row types the number of stairs directly: every stair has one tread and one riser. The riser, tread, stair width and waste are the example's.
Questions
How much carpet do I need for 13 stairs?
Choose From a number of stairs, pick 13 stairs and type the riser height and tread run. Each stair takes its tread run plus its riser height, and the table lists the length and roll for several counts. The stair width, waste allowance and roll width are the example's until you change them.
What is the length of carpet for one step?
The tread run plus the riser height, plus any nosing wrap you add. The calculator adds the treads and the risers separately, so a flight whose top is the floor above has one tread fewer than risers.
Why does the roll length differ from the length covered?
The waste allowance is added once to the length covered, and a stair wider than the roll takes more than one strip. The roll length is the covered length with waste, times the strips across the stair width.
Local codes and amendments differ; your building department decides.
Sources (2)
-
2021 International Residential Code, Chapter 3 Building Planning (opens in new tab), International Code Council, 2021 IRC.
Code or government.
“The riser height shall be not more than 7 3/4 inches (196 mm).”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1) -
Finding the Right Carpet (opens in new tab), The Carpet and Rug Institute, web page, undated.
Standards or industry body.
“Broadloom carpet can be 12 feet, 13.5 feet, or 15 feet in width.”
Checked November 12, 2026. Figures and codes change; verify with the source.
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.
Sources
- [1] International Code Council, 2021 International Residential Code, Chapter 3 Building Planning. Checked November 12, 2026. https://codes.iccsafe.org/content/IRC2021P2/chapter-3-building-planning
- [2] The Carpet and Rug Institute, Finding the Right Carpet. Checked November 12, 2026. https://carpet-rug.org/carpet-for-business/finding-the-right-carpet/