From measured space to purchasable material
Carpet on stairs follows each tread and riser rather than the horizontal staircase footprint. This calculator adds those two dimensions, allows extra length at each step for the intended nosing treatment, and multiplies by the number of covered steps. A landing contributes separate rectangular area. It also checks how many stair-width strips fit across a carpet roll and estimates the roll length when the step pieces are divided evenly among those strips. The model assumes simple repeated straight steps. Winders, curved stairs, pattern matching, and continuous pile orientation need a separate cutting plan.
Measure, select yield and round the order
- Count only steps receiving carpet and measure the covered width.
- Measure along the tread and riser path and add treatment-specific trim.
- Enter landing dimensions separately and confirm the strip cutting plan with the installer.
Net requirement and purchase calculation
A worked example
Twelve steps × 36 × (10 + 7.5 + 1.5) inches ÷ 144 = 57 sq ft. With 10% allowance, the area estimate is 62.7 sq ft; four 36-inch strips fit across a 12 ft roll.
Carpet for Stairs: what changes the result?
Separate installed coverage from the material you can purchase. The comparisons below are calculated from this page’s default example. Each row changes only the named input; all other inputs stay at their displayed example values. These are mathematical scenarios, not measurements from a completed project.
| Changed assumption | Default input | Comparison input | Result: default → comparison |
|---|---|---|---|
| Number of covered steps | 12 | 13 | Net material area with allowance: 62.7 → 67.925 sq ft Minimum step-strip roll length: 4.75 → 6.3333 ft |
| Carpeted stair width | 36 in | 43.2 in | Net material area with allowance: 62.7 → 75.24 sq ft Minimum step-strip roll length: 4.75 → 6.3333 ft |
| Tread depth | 10 in | 12 in | Net material area with allowance: 62.7 → 69.3 sq ft Minimum step-strip roll length: 4.75 → 5.25 ft |
| Riser height | 7.5 in | 9 in | Net material area with allowance: 62.7 → 67.65 sq ft Minimum step-strip roll length: 4.75 → 5.125 ft |
Displayed values are rounded. Whole-pack results change in steps; continuous quantities may change before a new pack is needed. To compare your actual project, enter your dimensions above, save a scenario, then change one assumption.
Coverage, allowance and purchasing limits
- The area result and minimum step-strip roll length are different measures; the area price result is not a guaranteed roll-order cost.
- The roll-width strip arrangement assumes step pieces may be separated; a continuous stair runner requires a different plan.
- Do not use this simple rectangular model for winders or curved stairs.
Frequently asked questions
How much carpet do I need for 12 straight stairs?
At 36 inches wide, with 10-inch treads, 7.5-inch risers, and 1.5-inch extra per step, the repeated surface is 57 sq ft; 10% extra makes 62.7 sq ft.
Does this include a stair landing?
Yes, a rectangular landing can be added by length and width, but its roll cutting layout is separate.
Should carpet follow the stair nosing?
That depends on the installation treatment. Measure the intended path and enter the additional per-step length.
Calculation method: JICWH methodology. Examples are planning assumptions, not product recommendations.