Carpet Underlay/Pad Quantity Calculator

Roll & Global Settings

Roll Width(ft or m)

Roll Length(ft or m)

Waste Factor%

Price per Rolloptional

Rooms

Add rectangular spaces. Dimensions use the chosen unit.

Name	Length	Width	Action

Landings

Add intermediate platforms.

Name	Length	Width	Action

Straight Stairs

Estimate for a straight run. For complex winders, add custom rectangles approximating each wedge or use a more detailed stair tool.

Stair Width

Steps (count)

Tread Depth

Riser Height

Nosing Wrap Allow.

Cover risers

Custom Pieces

Add any extra rectangles (e.g., odd shapes approximated as rectangles).

Name	Length	Width	Action

Results

Unit System

Rooms Area

Landings Area

Stairs Area

Custom Area

Subtotal Area

Waste Factor

Total Area incl. Waste

Roll Area

Linear Feet Needed

Rolls Needed (ceil)

Estimated Material Cost

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Example Data Table

Area	Length	Width	Notes
Bedroom	12 ft	10 ft	Rectangular room
Hall	15 ft	6 ft	Narrow corridor
Upper Landing	6 ft	3 ft	Platform
Stairs	13 steps	3 ft	10 in tread, 7.5 in riser
Closet	5 ft	4 ft	Custom piece

Formula Used

Rectangles Area = Length × Width

Stairs Area per step = Stair Width × (Tread Depth + (Cover Risers ? Riser Height : 0) + Nosing Wrap).

Stairs total = Area per step × Number of steps.

Subtotal area = Rooms + Landings + Stairs + Custom pieces.

Total with waste = Subtotal × (1 + Waste% ÷ 100).

Roll area = Roll Width × Roll Length.

Linear feet needed = Total with waste ÷ Roll Width.

Rolls needed = ceil(Total with waste ÷ Roll area).

How to Use This Calculator

Select your preferred units.
Enter roll width and length. Defaults reflect common residential products.
Add rooms and landings using their finished dimensions.
For stairs, provide width, count, tread depth, riser height, and any nosing wrap allowance. Toggle “Cover risers” if applicable.
Adjust waste percentage to account for offcuts, pattern matching, and on‑site realities.
(Optional) Provide price per roll to see estimated material cost.
Review results, then export CSV or PDF for records and quoting.

FAQs

1) What roll width should I use?

Many underlays come in 6 ft (1.83 m) or 4 ft (1.22 m) widths, and lengths like 45 ft (13.7 m) or 60 ft (18.3 m). Use the actual spec from your supplier for best accuracy.

2) How much waste should I allow?

10–15% is common for simple layouts; complex stairs or many obstacles can require 15–25%+ waste. This tool lets you set any percentage to match site conditions.

3) Do I need to cover risers with underlay?

Practices vary. Some installers use underlay on treads only, others include risers for comfort and acoustics. Toggle the option to see both scenarios and follow local codes and vendor guidance.

4) Can I use this for metric projects?

Yes. Switch to metric and enter roll and space dimensions in meters or centimeters equivalents. Results will be shown consistently in metric.

5) How accurate is the stairs estimate?

It’s a practical estimator for straight flights. For winders or curved stairs, add custom rectangles approximating each wedge, or use a dedicated stair geometry tool for higher precision.