Quick answer
Carpet strips = ⌈room dimension ÷ roll width⌉, and the carpet bought = strips × the other dimension × roll width. A 14 × 11 ft room on a 12 ft roll needs one 14 ft strip: 168 ft² or 18.67 yd² for a 17.11 yd² room.
Enter the room size and roll width. The calculator returns carpet needed, linear feet of roll and room area.
Related tools: Tile Calculator: Number of tiles (and boxes) for an area. Flooring Calculator: Flooring area with waste, and boxes if you know the coverage per box. Cost to Tile a Shower Calculator: Estimated cost from tiled area, material price and labor price.
How to use the Carpet Calculator
- Enter room length (ft) (above 0).
- Enter room width (ft) (above 0).
- Choose roll width: 12 ft and 15 ft.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Room length | A number, in ft | > 0 |
| Room width | A number, in ft | > 0 |
| Roll width | Choose one: 12 ft; 15 ft | Starts at 12 ft |
Formula and method
Formula
strips = ⌈room dimension ÷ roll width⌉; carpet area = strips × other dimension × roll width
IEEE-754 double precision; shown to the decimals indicated.
Compares laying strips along the length or along the width and uses the smaller area; seams, pattern match and pile direction are not included. Plan geometry only; confirm quantities with your supplier and local code before ordering.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Room length = 14; Room width = 11; Roll width = 12 ft.
| Result | Value |
|---|---|
| Carpet needed | 18.67 yd² |
| Linear feet of roll | 14 |
| Room area | 17.11 yd² |
Example 2
Inputs: Room length = 16; Room width = 13; Roll width = 15 ft.
| Result | Value |
|---|---|
| Carpet needed | 26.67 yd² |
| Linear feet of roll | 16 |
| Room area | 23.11 yd² |
Example 3
Inputs: Room length = 10; Room width = 25; Roll width = 12 ft.
| Result | Value |
|---|---|
| Carpet needed | 33.33 yd² |
| Linear feet of roll | 25 |
| Room area | 27.78 yd² |
The first line is the headline result (carpet needed). Below it the carpet Calculator lists linear feet of roll and room area, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Why you buy more than the room
Carpet comes in fixed widths, usually 12 ft. The 11 ft width fits one strip but the 12 ft roll is wider, so the extra foot is waste. Choosing which way to run the roll can cut waste.
Extras
Add extra for patterned carpet that must match, for stairs, and for seams across the room. Many fitters add 10% for cuts. The calculator gives the minimum for a rectangular room.
How the result changes with room length
Holding every other input at the first worked example, this table changes only room length. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Room length | Carpet needed | Linear feet of roll | Room area |
|---|---|---|---|
| 7 | 9.33 yd² | 7 | 8.56 yd² |
| 14 | 18.67 yd² | 14 | 17.11 yd² |
| 28 | 37.33 yd² | 28 | 34.22 yd² |
| 56 | 73.33 yd² | 55 | 68.44 yd² |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Room length: entering "0" shows "Room length must be greater than 0." beside that field and no result.
- Room width: entering "0" shows "Room width must be greater than 0." beside that field and no result.
Choosing between the Carpet Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Tile Calculator](/construction/tile-calculator/) | area to tile, tile length and tile width | Tiles needed |
| [Flooring Calculator](/construction/flooring-calculator/) | room length, room width and waste allowance | Flooring to buy |
| [Cost to Tile a Shower Calculator](/construction/cost-to-tile-shower/) | area to tile, tile price and labor and setting materials | Estimated cost |
| [Tile Grout Calculator](/construction/tile-grout-calculator/) | area, tile length and tile width | Grout volume |
| [Roof Pitch Calculator](/construction/roof-pitch-calculator/) | i know the and value | Pitch |
Background: construction estimates
Material quantities are geometry plus a margin. Calculate the exact volume or area, add an allowance for waste, spillage, cuts and uneven ground (calculator pages commonly mention 5 to 10 percent, a rule of thumb that varies by material and job) and round up to whole units. One cubic yard is exactly 27 cubic feet.
Suppliers often have minimum order sizes and may charge for small loads, so confirm quantities, product yields and local code with your supplier or a qualified estimator before ordering.
Assumptions and limitations
- Add extra for patterned carpet
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for room length and room width to confirm this.
Frequently asked questions
What is the standard roll width?
12 ft in the US; 4 m or 5 m in many countries.
How do I convert to square yards?
Divide square feet by 9.
Do I need underlay?
Underlay is bought for the room area.
What does the Carpet Calculator calculate?
Square yards of broadloom carpet for a room, choosing the layout that wastes least. It returns Carpet needed, Linear feet of roll and Room area.
What formula does the Carpet Calculator use?
strips = ⌈room dimension ÷ roll width⌉; carpet area = strips × other dimension × roll width. Compares laying strips along the length or along the width and uses the smaller area; seams, pattern match and pile direction are not included.
What do I need to enter in the carpet Calculator?
You enter Room length (ft), Room width (ft) and Roll width.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Add extra for patterned carpet.
What does the “Roll width” option change?
It sets how the carpet is worked out. The choices are 12 ft and 15 ft.
What is an example of a carpet result?
With room length 14, room width 11 and roll width 12 ft, the carpet needed is 18.67 yd².
Can I rely on this calculator for a decision?
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work. For this calculator in particular: Add extra for patterned carpet.
Related calculators
- Tile Calculator — Number of tiles (and boxes) for an area.
- Flooring Calculator — Flooring area with waste, and boxes if you know the coverage per box.
- Cost to Tile a Shower Calculator — Estimated cost from tiled area, material price and labor price.
- Tile Grout Calculator — Volume of grout needed for a tiled area.
- Roof Pitch Calculator — Roof pitch as rise per 12 inches, angle, slope percent and rafter length factor.
- Aquarium Volume Calculator — Capacity and filled weight of a rectangular aquarium.
- Construction Waste Calculator — Material to order after a waste allowance.
- Taper Calculator — Taper ratio and angle from large diameter, small diameter and length.
Sources
- OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B conversion factors (international foot 0.3048 m, inch 25.4 mm, US gallon 3.785411784 L)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.