Carpet Calculator

Enter the room dimensions and roll width, add a waste allowance, and get the area to order and an optional cost.

Underlay and gripper are calculated alongside so nothing gets left off the order.

How to use the carpet calculator

Enter the room dimensions.

Set the roll width and waste allowance.

Read square yards, metres and cost.

Why use the Build Tally carpet calculator

Roll width aware

Shows the area you will actually be billed for.

Square yards and metres

Both units, side by side.

Underlay and gripper

Calculated from area and perimeter.

Multiple rooms

Add sections and total them.

Square yards, roll widths and why they differ

Carpet in North America is still often priced by the square yard — 9 square feet — while most other markets use the square metre. Carpet also comes on rolls of a fixed width, commonly 12 ft or 15 ft (or 4 m and 5 m), and that width drives the real waste. A room 13 ft wide from a 12 ft roll needs a seam and a strip, and you pay for the full roll width across the room's length either way. Entering the roll width gives you the number you will actually be charged for rather than the theoretical area.

Seams, pile direction and stairs

Seams should run along the length of the room and away from the main sightline where possible, never across a doorway. Pile direction must be consistent across every piece or the two halves will read as different shades under the same light, which is why offcuts cannot simply be rotated to fit. Stairs are measured separately: allow the tread depth plus the riser height plus a couple of inches per step, and add extra if the carpet has a pattern to match.

Underlay, gripper and fitting

Underlay is normally ordered to the same area as the carpet and makes a bigger difference to how a floor feels and wears than most people expect — a good underlay under a mid-range carpet usually beats the reverse. Gripper is measured as the room perimeter less door openings. If you are getting the carpet fitted, ask whether the quote includes uplift and disposal of the old floor, door trimming and thresholds; those extras add up.

Read the guide: How to Calculate Square Footage of a Room, a House or a Yard

Frequently asked questions

How do I calculate carpet for a room?

Multiply length by width for square feet, then divide by 9 for square yards. Enter roll width above and the calculator allows for it.

How many square feet in a square yard of carpet?

Nine. A square yard is three feet by three feet.

What carpet roll widths are available?

Twelve feet is the most common, with 15 ft also widely stocked. Metric markets use 4 m and 5 m rolls.

How much carpet waste should I allow?

Ten percent for a simple room. More where seams are needed or the carpet has a pattern to match.

Do I need new underlay?

Usually yes. It wears out, and fitting a new carpet over compressed old underlay wastes most of the benefit of the new carpet.

How do I measure carpet for stairs?

Per step: tread depth plus riser height plus about two inches. Multiply by the number of steps and add extra for pattern matching.