Carpet comes in fixed widths, so a room’s square footage is only part of the order. This estimate compares two simple strip directions and includes your allowance in both the roll length and billed area.
It assumes either pile direction is acceptable. Ask your fitter to confirm seams, doorways, pattern matching and any offcut reuse before the carpet is cut.
How to use this calculator
- Measure the room including into doorways and bay windows — carpet runs into every recess.
- Decide the roll direction, keeping seams out of main walkways and running them away from windows.
- Choose the roll width that covers the room's shorter cross-dimension in a single drop if possible.
- Calculate, and discuss the cutting plan with the store — a good fitter can often use offcuts on stairs or in closets.
How carpet quantities are calculated
Area in square yards = square feet / 9. Compare both rectangular strip layouts: ceiling(room width / roll width) x room length, and ceiling(room length / roll width) x room width. Use the smaller total roll length, then add the chosen allowance. Billed area = total roll length x roll width. This estimate assumes either pile direction is acceptable and does not optimise offcut reuse; a fitter must confirm seams and pile direction.
A 12 ft x 11 ft bedroom is 132 sq ft, or 14.67 square yards. Off a 12 ft roll you order an 11 ft length plus allowance, and you are billed for the full 12 ft width — roughly 145 sq ft with the 10 percent allowance included.
A few things worth checking
- Quoting the room area in square feet to a store that prices in square yards, and misreading the total by a factor of nine.
- Ignoring the roll width and budgeting for the exact room area, then being surprised by the billed offcut.
- Running a seam across the doorway or the main path between door and window, where wear opens it up first.
Your questions, answered
Why is the billed area bigger than my room?
The estimate uses full roll widths, so supplied carpet can include area that will be cut away. It compares two rectangular orientations, chooses the smaller total roll length and then adds your allowance. It does not optimise reuse of those offcuts.
Does this also calculate underlay?
No. The output is carpet roll length and approximate billed carpet area. Underlay coverage and any separate allowances need their own check against the fitting plan and product instructions.
Can carpet offcuts be reused elsewhere?
They may be usable, but this calculation does not lay out or reuse them. Ask your fitter to check each offcut against the required dimensions, joins, pattern and pile direction before reducing an order.
Does the calculator choose the right pile direction?
It assumes either of the two rectangular orientations is acceptable and selects the one using less roll length. A fitter must confirm pile direction and seam placement. The lower figure may not suit every carpet or room.
A Simple Materials Checklist for Your Next DIY Project
Keep the measurements, materials and small forgotten bits on one page before you shop.