Stair Carpet Calculator
Required Material
What Is a Stair Carpet Calculator?
A stair carpet calculator is a digital tool that estimates how much carpet is required for a staircase. Instead of rough estimates, it uses exact measurements like:
- Number of steps
- Stair width
- Tread depth
- Riser height
- Nosing overhang
- Installation style
- Waste allowance
By combining these inputs, the calculator outputs:
- Total linear carpet length
- Total carpet area in square feet and square yards
- Per-step carpet usage
This is useful for homeowners, installers, and contractors who want accuracy before buying carpet.
Why Stair Carpet Calculations Are Tricky
Stairs are not flat surfaces. Each step has multiple parts, and carpet must wrap, bend, and sometimes tuck around edges. Small miscalculations add up fast.
Common problems include:
- Forgetting riser height
- Ignoring nosing overhang
- Underestimating waste
- Choosing the wrong installation style
A stair carpet calculator handles these details for you.
Key Stair Terms Explained in Plain English
Understanding the inputs helps you use the calculator correctly.
Number of Steps
This is the total count of risers, not treads. If you have 13 vertical rises, enter 13.
Stair Width
Measured from wall to wall or edge to edge. Most residential stairs are around 36 inches wide.
Tread Depth
The flat part where you step. This is usually 9 to 11 inches.
Riser Height
The vertical height between steps. Standard risers are often around 7 to 8 inches.
Nosing Overhang
The part of the tread that sticks out over the riser. Carpet must wrap around this edge.
Top Landing Length
Optional. This adds extra carpet if the carpet continues onto the landing at the top of the stairs.
Waste Factor
Extra material added to account for trimming, pattern matching, and installation errors. Ten percent is a common and safe choice.
Installation Styles: Waterfall vs Hollywood
The calculator lets you choose between two stair carpet installation styles. This choice affects how much carpet is used per step.
Waterfall Style
- Carpet drapes over the stair edge
- No tight tuck under the nosing
- Uses less carpet per step
- Faster to install
Hollywood Style
- Carpet wraps tightly around the nosing
- Creates a tailored, crisp look
- Uses about 1.5 to 2 inches more carpet per step
- More precise installation
The calculator automatically adjusts carpet length based on the style you choose.
How This Stair Carpet Calculator Works
This calculator follows a logical step-by-step process.
Step 1: Calculate Carpet Length Per Step
For each step, the calculator adds:
- Tread depth
- Riser height
- Nosing allowance (varies by style)
- Padding allowance (1 inch for comfort and fit)
Step 2: Multiply by Number of Steps
The per-step length is multiplied by the total number of steps.
Step 3: Add Landing Length
If you enter a top landing length, it is added to the total.
Step 4: Apply Waste Factor
The total length is increased by the selected waste percentage.
Step 5: Convert Units
The calculator converts:
- Inches to feet and inches for linear length
- Square inches to square feet
- Square feet to square yards
This gives results that match how carpet is sold.
Understanding the Results
After clicking Calculate Carpet, you will see three main results.
Total Linear Length (Runner)
This shows how long the carpet needs to be from top to bottom, displayed in feet and inches.
Total Area (Broadloom)
This shows how much carpet area you need:
- Square yards for ordering
- Square feet for easy comparison
Install Details
This explains how much carpet is used per step and confirms the installation style.
These results help you talk confidently with suppliers and installers.
Example Calculation
Imagine this staircase:
- 13 steps
- 36-inch width
- 10-inch tread
- 7.5-inch riser
- 1.25-inch nosing
- Hollywood style
- 10 percent waste
The calculator:
- Adds extra length for tight wrapping
- Includes padding allowance
- Applies waste for safety
The final output shows exactly how much carpet to order, with no guesswork.
Who Should Use a Stair Carpet Calculator?
This tool is useful for:
- Homeowners planning a remodel
- DIY installers
- Flooring contractors
- Interior designers
- Property managers
Anyone buying stair carpet benefits from accurate numbers.
Benefits of Using This Calculator
- Prevents underbuying carpet
- Reduces expensive overbuying
- Accounts for real-world installation details
- Saves time and planning effort
- Easy to use with clear inputs
It is far more reliable than manual estimates.