Carpet Calculator
Work out how much carpet you need for a room. Enter the room length and width, the carpet roll width, and how much wastage to allow, and this calculator gives the area to order plus how many metres of roll you'll need.
Formula
Area = Length × Width; With Wastage = Area × (1 + Wastage/100)
- Room area = length × width.
- Area with wastage = room area × (1 + wastage% / 100) to allow for cutting, fitting and pattern matching.
- Most carpet is sold by the metre off a roll, so the calculator divides your area (with wastage) by the roll width to get the length you need.
- Standard carpet roll widths are 3 m, 3.66 m (12′), or 4 m; pick the one closest to your room width to minimise waste.
- A 10% wastage allowance is typical; add more for complex room shapes or patterned carpet that needs matching.
5 m × 4 m room, 4 m roll, 10% wastage
Inputs
- Room Length: 5 m
- Room Width: 4 m
- Carpet Roll Width: 4 m
- Wastage: 10 %
Room area = 20 m². With 10% wastage = 22 m². Roll length needed = 22 ÷ 4 = 5.5 m, so order 5.5 m of 4-metre-wide carpet.
Frequently asked questions
Why do I need to add wastage?
Cutting and fitting always waste some carpet, and patterned carpets need extra for matching. A 10% buffer is standard; bump it to 15% for irregular rooms or patterns.
What is a carpet roll width?
Carpet is sold off rolls, typically 3 m, 3.66 m (12 feet), or 4 m wide. Choose a roll width that fits your room to avoid joins or excessive waste.
Can I join two pieces to cover a wider room?
Yes, but seams are visible and less durable. If your room is wider than available rolls, plan the join carefully (ideally under furniture or low-traffic areas).
Does this calculator account for doorways or odd shapes?
No. Measure the full rectangular area and let the fitter trim around obstacles, or subtract those areas yourself before using the calculator.
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