What is a carpet calculator?
A carpet calculator is a free online tool that turns the dimensions of a room and a unit price into two useful figures: the total area of carpet you need to buy and the total cost of that carpet. It multiplies the room length by the room width to get the floor area, adds a wastage allowance for offcuts and pattern matching, and then multiplies the result by the price per unit area. Because it works in both metric and imperial units, you can measure in metres or feet and price the carpet per square metre or per square foot, and the calculator keeps everything consistent for you. It is handy for homeowners planning a single room, landlords fitting out a rental, and installers preparing a quick quote.
How does the calculator work?
Enter the room length and room width, choose the units you measured in, set the price per unit area, and adjust the wastage percentage if you need to. The calculator returns the total carpet area — including the wastage allowance — and the total cost. You can switch the area result between square metres and square feet at any time, and the cost updates instantly whenever you change an input.
The floor area is simply length times width:
Carpet is rarely fitted with zero offcuts, so a wastage percentage is added to cover trimming, seams and pattern repeats:
Finally, the total cost is the area you actually buy multiplied by the price per unit area:
Worked example
Suppose a room measures 5 m long by 4 m wide, you allow 10% for wastage, and the carpet is priced at 25 per square metre.
First, the raw floor area:
Adding the 10% wastage allowance:
Multiplying by the unit price gives the total cost:
So you would buy 22 m² of carpet at a total cost of 550.
Practical notes
- Choose a realistic wastage figure: 5% to 10% is typical for a plain carpet in a simple rectangular room, but large patterns, stairs, and awkward layouts can push wastage to 15% or more.
- Measure the widest points: Take the length and width at the longest and widest parts of the room, including doorways and alcoves, so the carpet reaches every corner.
- Mind the roll width: Carpet is sold from rolls of a fixed width, so the practical amount you must buy can exceed the calculated area; use the estimate as a starting point and confirm with your supplier.
- Keep price and area units matched: You can price per square metre or per square foot — the calculator converts internally, so enter the price in whichever unit your quote uses.
FAQs
How much carpet do I need for a room?
Multiply the room length by the width to get the floor area, then add a wastage allowance. For a 5 m by 4 m room with 10% wastage that is 5 × 4 × 1.10 = 22 m² of carpet.
Why should I add wastage?
Fitting a carpet almost always produces offcuts around edges, doorways and seams, and patterned carpet needs extra length so the design lines up. A wastage allowance makes sure you order enough rather than coming up short.
Can I use square feet instead of square metres?
Yes. Measure the room in feet, price the carpet per square foot, and switch the area result to square feet. The calculator handles the conversion between metric and imperial units for you.
Does the total cost include underlay or fitting?
No. This calculator estimates the cost of the carpet material only. Add underlay, gripper rods, door bars and installation labour separately when budgeting for the whole job.