What is the Carpet Calculator?
The Carpet Calculator estimates how much carpet you need to cover a room. Enter the room's length and width in feet, choose a waste allowance, and it returns the total carpet required in both square feet and square yards. If you supply a price per square foot, it also estimates your total material cost.
How to use it
Measure your room at its longest and widest points and enter both values in feet. Add a waste percentage — most installers recommend 5–10% for straight rooms and up to 20% for rooms with many corners, closets, or patterned carpet that must be matched. Optionally enter the carpet price per square foot to get a budget figure.
The formula explained
The base floor area is simply length × width. Because carpet must be cut, seamed, and trimmed, you rarely use exactly the floor area, so we multiply by a waste factor: area × (1 + waste% ÷ 100). Since carpet is frequently priced by the square yard, we also divide the square footage by 9 (there are 9 square feet in a square yard).
$$A = L \times W \times \left(1 + \frac{P}{100}\right)$$ $$\text{where}\quad \left\{ \begin{aligned} L &= \text{Length (ft)} \\ W &= \text{Width (ft)} \\ P &= \text{Waste (\%)} \end{aligned} \right.$$ $$\text{Square Yards} = \frac{\text{Length} \times \text{Width} \times \left(1 + \frac{\text{Waste (\%)}}{100}\right)}{9}$$ $$\text{Total Cost} = \text{Length} \times \text{Width} \times \left(1 + \frac{\text{Waste (\%)}}{100}\right) \times \text{Price/ft}^2$$
Worked example
For a 12 ft × 10 ft room with a 10% waste allowance: base area = \(12 \times 10 = 120\) sq ft. With waste = \(120 \times 1.10 = \mathbf{132}\) sq ft, which is \(132 \div 9 \approx 14.67\) square yards. At $3.50 per square foot the estimated cost is \(132 \times 3.50 = \$462\).
FAQ
How much waste should I add? A 10% allowance suits most rectangular rooms; increase it for irregular layouts or large-repeat patterns.
Why square yards? Many carpet rolls and price lists are quoted per square yard, so the conversion makes ordering easier.
Does this include padding or stairs? No — this estimates floor carpet only. Add padding and stair treads separately.
