How much waste should I add for carpet?

10% is a common starting point for simple rooms. Add more for patterned carpet, lots of doorways, closets, or irregular layouts.

What is the typical roll width for broadloom carpet?

A very common broadloom width is 12 feet (about 3.66 m). In many markets, 4 m rolls are also common. Confirm the exact width with your supplier.

Should I buy carpet by square feet or square yards?

Both are used. Many suppliers quote broadloom in square yards, while installers may measure in square feet. This calculator shows both so you can compare quotes.

Carpet Calculator (Broadloom & Tiles)

Carpet Calculator

Estimate how much carpet to buy for a room. Choose broadloom roll goods (by roll width) or carpet tiles (by tile size), apply a waste allowance, and optionally estimate material cost using a price per area. You can also enter a total net area if you already have it.

Carpet Calculator

Broadloom roll goods or carpet tiles with waste allowance

Carpet type

Input method

Quantity (same-size rooms)

Currency

Price per area (optional)

Room length

Room width

Openings area (optional)

Waste allowance

Roll width

Results

Enter dimensions above to calculate

Formulas used

Carpet estimates are mainly area-based. Broadloom roll goods also depend on roll width and how many runs are needed to cover the room.

1. Room Area

Formula:

Gross Area = Length × Width

Start with the room footprint (length × width). If you already know your total net area, you can enter that directly in the calculator. If you have openings you don’t plan to carpet, subtract their area to get net area.

2. Waste Allowance

Formula:

Order Area = Net Area × (1 + Waste%)

Waste covers trimming, fitting around jambs, pattern alignment, and installation errors. 10% is a common baseline; patterned carpet often needs more.

3. Broadloom Roll Goods (If Selected)

Formula:

Runs = ceil(Room Width / Roll Width), Length = Runs × Room Length

Broadloom is cut from a fixed roll width (often 12 ft / 3.66 m or 4 m). The calculator estimates roll length by choosing the better of two orientations (rotate the room 90°) to reduce seams and waste.

4. Carpet Tiles (If Selected)

Formula:

Tiles = ceil(Order Area / Tile Area)

Carpet tiles are estimated by area: find the order area, then divide by the tile area and round up to whole tiles.

5. Cost (Optional)

Formula:

Estimated Cost = Order Area × Price per Area

If you enter a price per area, the calculator will estimate material cost using the order area (including waste). Switch currency to match your quote.

Example

A 5 m × 4 m room, 10% waste. Broadloom roll width 4 m, or 500 mm × 500 mm carpet tiles.

Net area = 5 × 4 = 20.0 m²
Order area = 20.0 × 1.10 = 22.0 m²
Broadloom (4 m roll): Order length ≈ 22.0 ÷ 4 = 5.5 m
Tiles (0.5 × 0.5 m): Tiles = ceil(22.0 ÷ 0.25) = 88
Optional cost (e.g. 25 / m²): 22.0 × 25 = 550

Frequently Asked Questions

How much waste should I add for carpet?: 10% is a common starting point for simple rooms. Add more for patterned carpet, lots of doorways, closets, or irregular layouts.
What is the typical roll width for broadloom carpet?: A very common broadloom width is 12 feet (about 3.66 m). In many markets, 4 m rolls are also common. Confirm the exact width with your supplier.
Should I buy carpet by square feet or square yards?: Both are used. Many suppliers quote broadloom in square yards, while installers may measure in square feet. This calculator shows both so you can compare quotes.