Carpet Calculator
Work out how much broadloom carpet to buy for a room, including linear metres, offcut waste, and total cost.
Room units
m
m
m
%
Linear metres of broadloom: 10.5 m
- 1
Room floor area
5 × 4 = 20 - 2
Strips across width (rounded up)
4 ÷ 3.66 = 2Full broadloom strips are needed across the width, so the count is rounded up. - 3
Linear metres with waste
2 × 5 × (1 + 0.05) = 10.5 - 4
Carpet area
10.5 × 3.66 = 38.43
How does this calculator work?
Carpet is bought off a fixed-width roll, so divide room width by the broadloom width and round up to get full-width strips. Multiply strips by room length, add a waste allowance, then multiply by the roll width for total area and by price for cost. Offcut waste is the area bought minus the floor area.
Formula
How this is calculated
Carpet is sold off a roll (broadloom) in a fixed width — most commonly 3.66 m (12 ft) or 4 m — so the amount you buy is driven by the roll width, not just the floor area. Enter the room length and width (in metres or feet), the broadloom width of your chosen carpet, a waste allowance, and an optional price per square metre. Feet are converted to metres at 0.3048 m/ft before any calculation.
The room is laid out in full-width strips running along its length. The number of strips is the room width divided by the broadloom width, rounded up to the next whole strip, because a part-width strip still consumes a full roll width. The linear length you must buy is the number of strips multiplied by the room length, then increased by the waste percentage to cover trimming, squaring up, and matching pattern repeats. Multiplying that linear length by the broadloom width gives the total carpet area purchased, and multiplying by the price gives the estimated cost.
Offcut waste is the difference between the carpet area bought and the actual floor area — it is unavoidable whenever the room width is not an exact multiple of the roll width. Use a higher waste percentage for patterned carpet or awkward, non-rectangular rooms. The estimate assumes a simple rectangular room and a single carpet direction; stairs, doorways, and seam placement may require extra material.
Frequently asked questions
Broadloom is carpet sold on a wide roll at a fixed width, typically 3.66 m (12 ft) or 4 m. You buy it by the linear metre off that roll, so the roll width determines how many strips a room needs.
Because the roll width rarely divides evenly into the room width, each strip is full-width and any extra is offcut. Added to the waste allowance for trimming and pattern matching, the purchased area is usually more than the bare floor area.
Around 5% is typical for plain carpet in a simple rectangular room. Allow 10% or more for patterned carpet, diagonal lay, stairs, or rooms with bays and alcoves.
Also known as
TG we-Calculate Editorial Team. (2026). Carpet Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/carpet-calculator
TG we-Calculate Editorial Team. "Carpet Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/carpet-calculator.
TG we-Calculate Editorial Team, "Carpet Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/carpet-calculator
@misc{wecalculate_carpet_calculator, title = {Carpet Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/carpet-calculator}}, year = {2026}, note = {TG we-Calculate} }
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