Carpet Calculator — How Much Carpet Do I Need?
Calculate exactly how much carpet to order, including the right number of drops for your roll width.
How much carpet do I need?
Most people start by measuring the room area, but carpet is sold from a roll with a fixed width. That means you may need more carpet than the raw length x width area suggests. This calculator works out how many full-width drops you need, then adds waste so you can order a practical amount.
What is a carpet drop?
A drop is one length of carpet cut from the roll. If your room is wider than the roll, your fitter cuts multiple drops and joins them across the room.
How much waste should I add?
Add 10% for plain carpet in a simple rectangle. Use 15% for patterned carpet, pattern matching, alcoves, bay windows or L-shaped rooms. Use 20% for diagonal fitting because angled cuts waste more material.
Carpet roll widths explained
Standard carpet roll widths are 3m, 4m and 5m, with 4m the most common in the UK. Wider rolls can mean fewer joins, but not every supplier carries every width, so ask which rolls are available before you measure and order.
Linear metres vs square metres for carpet
Carpet shops often quote in linear metres, while area calculators give square metres. A linear metre is one metre of roll length, so the area depends on the roll width. This calculator shows both figures so you can compare quotes and order correctly.
Also useful:
Carpet calculator FAQ
Frequently Asked Questions
How do I calculate how much carpet I need?
Measure room length x width. Divide room width by roll width and round up to get number of drops. Multiply drops x length (plus 10% waste) to get linear metres. Multiply by roll width for total m².
What is a linear metre of carpet?
A linear metre is 1 metre cut from a roll of carpet. The total area depends on the roll width - 1 linear metre of 4m wide carpet = 4m².
How much carpet do I need for a 12x12 room?
A 12x12 foot room is 3.66m x 3.66m. On a 4m roll, you need 1 drop x 4.03m (with 10% waste) = 4.03 linear metres = 16.1m² of carpet.
Should I buy extra carpet for waste?
Always add at least 10%. Add 15% for patterned carpet, alcoves or bay windows. Add 20% for diagonal fitting.