Carpet on stairs wraps over the nose of every step, so each step uses its tread depth plus riser height plus an inch or two for the nosing. Carpet should be cut so the pile runs down the stairs. For a runner, you need one continuous length; for full-width carpet, you also need the stair width.
How to use the Stair Carpet Calculator
- Number of steps
- Tread depth
- Riser height
- Nosing wrap
- Stair (or runner) width
- Landing length (0 if none)
- Landing width
- Waste
- Carpet price
- Pad price
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the number of steps, tread depth, riser height, nosing allowance, stair width, landing size and prices.
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| Number of steps | A number |
| Tread depth | Units: in, cm, mm, ft, m |
| Riser height | Units: in, cm, mm, ft, m |
| Nosing wrap | Units: in, cm, mm, ft, m |
| Stair (or runner) width | Units: in, cm, mm, ft, m |
| Landing length (0 if none) | Units: ft, m, in, yd, cm |
| Landing width | Units: ft, m, in, yd, cm |
| Waste | In % |
| Carpet price | Units: /yd², /ft², /m² |
| Pad price | Units: /yd², /ft², /m² |
What each result means
- Runner length = [Number of steps]×([Tread depth] + [Riser height] + [Nosing wrap])
- Carpet area = ([Number of steps]×([Tread depth] + [Riser height] + [Nosing wrap])×[Stair (or runner) width] + [Landing length (0 if none)]×[Landing width])×(1 + [Waste]÷100)
- Cost (carpet + pad) = [Carpet area]×([Carpet price] + [Pad price])
Example values
How the main result changes when Number of steps changes and everything else stays at the example values above:
| Number of steps | Carpet area (ft²) |
|---|---|
| 6.5 | 34 |
| 9.75 | 50.9 |
| 13 | 67.9 |
| 16.25 | 84.9 |
| 19.5 | 101.9 |
| 26 | 135.9 |
Formula
Per step = (tread + riser + nosing wrap) × widthArea = steps × per step + landing; runner length = steps × (tread + riser + nosing)Worked example
Inputs — Number of steps: 13; Tread depth: 10 in; Riser height: 7.5 in; Nosing wrap: 1.5 in; Stair (or runner) width: 36 in; Landing length (0 if none): 0 ft; Landing width: 3 ft; Waste: 10 %; Carpet price: $30 /yd²; Pad price: $5 /yd².
Results — Runner length = 20.58 ft; Carpet area = 67.9 ft²; Cost (carpet + pad) = $264.15.
Frequently asked questions
How much carpet for 13 stairs?
With 10 in treads, 7½ in risers and 36 in width: about 20 ft of runner length, roughly 63 ft² (7 yd²) plus waste.
How much extra for the nosing?
About 1–2 in per step, depending on the shape of the nose and the carpet thickness.
Which way should the pile run on stairs?
Down the stairs, so it wears evenly and looks consistent.
What formula does the Stair Carpet Calculator use?
Per step = (tread + riser + nosing wrap) × width.