Carpet is one of the most expensive materials in a room makeover, and it’s sold in ways that make mental math genuinely tricky — square yards for broadloom, boxes for tiles, rolls with fixed widths. This carpet calculator cuts through all of that: enter your room dimensions and it estimates how much carpet you need in square feet and square yards, adds a realistic waste allowance for cutting and pattern matching, and breaks the result into broadloom rolls or carpet tiles depending on what you’re buying.
It matters because carpet waste isn’t like paint waste. Offcuts from a 12-foot-wide roll can’t be returned, and ordering 10% short can leave a bedroom half-finished with a dye lot that no longer matches. A proper estimate up front is the cheapest part of the whole project.
Whether you’re laying wall-to-wall carpet in a bedroom or going the DIY-friendly route, this page has you covered. If you’re weighing options first, read our carpet vs laminate comparison for bedrooms — and if you’ve decided on the easiest install of all, our guide on how to install peel-and-stick carpet tiles pairs perfectly with the tile estimate below.
How to Use the Carpet Calculator
- Enter the room dimensions. Measure length and width in feet (or metres) at the longest and widest points. For L-shaped rooms, split the room into two rectangles and add the results — the calculator has an option for that.
- Choose your carpet type. Broadloom (roll carpet, usually 12 ft wide), carpet tiles (typically 24 × 24 in or 50 × 50 cm), or peel-and-stick tiles. Each is estimated differently.
- Enter the roll width or tile size. Standard broadloom comes 12 ft wide (sometimes 15 ft); carpet tiles are most commonly 2 × 2 ft. The tool uses these to work out seams and cuts.
- Set the waste allowance. The default is 10% for simple rectangular rooms. Use 15% for rooms with lots of angles, closets, bay windows or pattern matching, and 5–7% is usually enough for plain carpet tiles in a square room.
- Decide on the laying direction. For broadloom, the calculator shows the most economical roll direction — seams should run toward the main light source and pile direction should be consistent, which the estimate accounts for.
- Read the buying quantities. For broadloom you get linear feet of roll and square yards (how carpet is priced); for tiles you get the tile count plus a few spares for future repairs. Round up to whole tiles or whole linear feet — suppliers don’t sell fractions.
How the Calculation Works
The starting point is floor area: length × width. For broadloom, the tool then works out how many strips of the fixed roll width are needed to cover the room’s width, multiplies by the room length (plus pattern match allowance for patterned carpet), and converts to square yards by dividing square feet by 9 — carpet is priced per square yard in the US and per square metre in the UK.
For carpet tiles, it’s simpler: room area ÷ tile area, rounded up, since tiles are modular — but the waste allowance still matters because edge cuts produce unusable offcuts. Patterned broadloom adds a pattern-repeat allowance to each strip, similar to wallpaper: each strip must be cut longer so the pattern aligns at the seam.
Worked example: a bedroom 12 ft × 14 ft = 168 sq ft = 18.7 sq yd. With 12-ft-wide broadloom: the 14-ft dimension needs two strips (12 ft + 2 ft from a second strip), each 12 ft long, so 24 linear feet of 12-ft roll = 288 sq ft = 32 sq yd before waste. With 10% waste, order about 35 square yards. As 2 × 2 ft tiles: 168 ÷ 4 = 42 tiles, plus 10% ≈ 47 tiles — buy a full box quantity above that.
Tips for Accurate Results
- Measure at the widest points, including doorways and alcoves. Carpet has to cover the floor that exists, not the rectangle you wish the room was.
- Add closets separately. A walk-in closet off a bedroom needs its own rectangle in the calculation — forgetting it is a classic way to come up short.
- Keep pile direction consistent. All broadloom strips must run the same way or the colour will look different across seams; plan the layout before you order.
- Buy spare tiles and keep them. Carpet tiles from the same dye lot stored flat will make future stain replacements invisible — 4–5 spares is a good rule.
- Don’t forget the underlay (pad). It’s estimated separately and usually sold by the roll or square yard; most rooms need the same area as the carpet itself.
- Check the pattern repeat on patterned carpet. Like wallpaper, a large repeat increases waste significantly — 15% allowance is the minimum there.
Frequently Asked Questions
How many square feet of carpet do I need for a 12×12 bedroom?
A 12 × 12 ft room is 144 sq ft, or 16 square yards before waste. With a standard 10% cutting allowance, plan on about 18 square yards of broadloom. For 2 × 2 ft carpet tiles that’s 36 tiles plus spares — so roughly 40–42 tiles depending on box size.
Is it cheaper to buy carpet tiles or broadloom?
Carpet tiles often cost more per square yard than basic broadloom, but they generate less waste in awkward rooms and you can install them yourself, saving labour costs. For a simple rectangular bedroom, broadloom is usually the cheaper material; for L-shaped rooms or DIY installs, tiles frequently win on total project cost.
How much extra carpet should I order for waste?
10% is the standard allowance for a rectangular room with plain carpet. Go to 15% for patterned carpet, rooms with bay windows or multiple doorways, and your first installation. Stairs need considerably more — typically measured tread by tread rather than by room area.
Can I install carpet tiles over my existing floor?
In most cases, yes — carpet tiles (especially peel-and-stick) go down well over clean, flat surfaces like plywood, concrete, vinyl or laminate. The floor must be dry, level and free of loose material. Our peel-and-stick carpet tile installation guide walks through the surface prep step by step.
Do I need to account for the carpet going under the skirting boards?
For wall-to-wall broadloom, professional installers tuck the carpet edge under the skirting (baseboard), which needs an extra inch or two per wall — the calculator’s waste allowance covers this. For carpet tiles, cut tiles to meet the skirting neatly instead; there’s no tucking involved.