Work out how much carpet your stairs need. Enter the number of steps, the tread depth, riser height and stair width, plus any landing, to get the square yards and roll length for wall-to-wall carpet, or the length of a stair runner, with padding and tack strip.
Last updated:
Units
Install
Stairs
Count every tread that gets carpet; a landing is entered below
in
cm
in
Front of nose to riser behind
cm
in
cm
in
Extra per step to wrap the nosing; 1–2 in
cm
in
Common: 22, 27, 31 in; leaves 3–5 in of wood each side
cm
Landing
in
In the direction you walk
cm
In the direction you walk
in
cm
Extras
%
$
$
Enter your values to see the result.
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How to use the Stair Carpet Calculator
Choose wall-to-wall or runner and inches or centimeters.
Enter the number of steps, stair width, tread depth and riser height.
Add any landings and the nose wrap allowance.
Pick the roll width (or the runner width) and a waste allowance.
Read the square yards or runner length, padding and tack strip.
How stair carpet is calculated
Carpet per step = tread depth + riser height + nose wrap allowance
Steps across the roll = roll width ÷ stair width, rounded down
Roll length = ⌈steps ÷ steps across⌉ × carpet per step, plus landings and waste
Square yards to buy = roll length × roll width ÷ 1,296 (in²) or ÷ 9 (ft²)
Runner length = steps × carpet per step + landing depths + trim allowance
Example: 13 steps, 36 in wide, 10 in treads, 7.5 in risers, 1.5 in wrap. Each step needs 19 in; 4 steps fit across a 12 ft (144 in) roll, so 4 strips × 19 in = 76 in, about 6 ft 4 in of roll. With 5% waste that is 79.8 in × 144 in = 8.9 sq yd.
Carpet per step at common sizes (36 in wide stair)
Tread × riser
Carpet per step
Sq yd per step (net)
27 in runner per step
10 × 7.5 in
19 in
0.53
1 ft 7 in
10 × 7.75 in
19.25 in
0.53
1 ft 7.25 in
11 × 7 in
19.5 in
0.54
1 ft 7.5 in
11 × 7.5 in
20 in
0.56
1 ft 8 in
12 × 6.5 in
20 in
0.56
1 ft 8 in
Values include a 1.5 in nose wrap. Installers may cut each step separately or run continuous strips; the material used is similar.
Tips
Choose a dense, low-pile carpet for stairs; it wraps the nose neatly and wears better.
Keep the pile direction running down the stairs on every step so the color looks the same.
Buy all carpet from one dye lot, and keep offcuts for future repairs.
Frequently asked questions
How much carpet do I need for 13 stairs?
For a typical 36 in wide stair with 10 in treads and 7.5 in risers, each step needs about 19 in of carpet including the nose wrap. Four steps fit across a 12 ft roll, so 13 steps take 4 strips, about 6 ft 4 in of roll, or roughly 8.4 sq yd to buy (about 9 sq yd with waste). The carpet actually on the stairs is about 6.9 sq yd.
How do you measure stairs for carpet?
Measure the stair width wall to wall, the tread depth from the front of the nose to the riser behind it, and the riser height. Add about 1–2 in per step to wrap the nose. Measure landings separately as rectangles.
Why do I have to buy more carpet than the stairs cover?
Carpet comes on rolls 12 or 15 ft wide, and each step is cut as a piece across the roll. Whatever width is left over after fitting whole steps becomes offcut, and the pile should run down the stairs, which limits how pieces can be turned.
How long should a stair runner be?
Multiply the number of steps by tread depth + riser height + about 1.5 in for the nose, add landings, then add a little for trimming. For 13 steps with 10 in treads and 7.5 in risers: 13 × 19 in = 247 in, about 21 ft before trimming allowance.
What width should a stair runner be?
A common choice leaves 3–5 in of wood showing on each side. On a 36 in stair, 27 in is the classic runner width; 31 in suits wider stairs and 22 in narrow ones.
Does carpet padding go on the risers?
Usually not. Padding is cut to cover the tread and wrap the nose, and it stops at the riser so the carpet can be tucked tight. Wall-to-wall stair carpet is held with tack strip at the back of each tread and the bottom of each riser.
Does this work for winding or open-sided stairs?
Treat winders and curved steps as separate pieces measured at their widest point, and add extra width for open sides where the carpet wraps the edge. A professional measure is wise for complex stairs.
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