Carpet Square Footage Calculator
If you are asking how much carpet do I need, the honest answer starts with square feet and ends with square yards. Enter each room's length and width below and this free carpet square footage calculator totals your area, converts it to square yards, and adds a waste allowance so you know how much carpet to buy — since carpet is sold by the square yard off 12-foot-wide rolls.
Enter your numbers
Your results
| Area with waste | — |
|---|---|
| Square yards, no waste | — |
| Square yards with waste | — |
| Waste allowance | — |
How to use this calculator
Measure each room's length and width in feet — run your tape measure along the longest walls. For an L-shaped room, split it into two rectangles on paper and measure each part separately.
Type the measurements into the room rows above. Press "+ Add room" to add bedrooms, hallways, closets, or stairs — the calculator adds everything together for you. Remove a room with the × button when you no longer need it.
Keep the waste allowance at 10% for normal rectangular rooms, or raise it to 15–20% for rooms with lots of corners, staircases, or a patterned carpet that must be matched at seams. Your results update instantly as you type.
How it works
The math is simple. Each room's area is length × width in square feet, and the total square footage is the sum of all rooms. Because carpet is sold by the square yard, the calculator divides the total by 9 (one square yard = 9 square feet). Finally it multiplies by (1 + waste %) to get the order quantity, and rounds up to a whole square yard — you can always keep offcuts, but you can't stretch carpet.
Assumptions: rooms are rectangular (or split into rectangles), measurements are in feet, and the waste factor covers cutting waste and odd shapes — not pattern matching or a directional layout, which needs a higher allowance. Results are estimates for planning and ordering; your installer does the final cut layout around the 12-foot roll width.
Example: a 12 × 15 ft room is 180 sq ft. Divide by 9 to get 20 sq yd. Add 10% waste (20 × 1.10) and you need 22 sq yd — which is exactly what the calculator shows with the default settings.
Frequently asked questions
How much carpet do I need for a 12x12 room?
A 12x12 ft room is 144 square feet, which divides by 9 to give exactly 16 square yards of carpet. Add the standard 10% waste allowance and you need about 17.6 square yards, so order 18 square yards to be safe.
Is carpet sold by the square foot or by the square yard?
Carpet is sold by the square yard, not the square foot. One square yard equals 9 square feet. Broadloom carpet comes on 12-foot-wide rolls, which is why installers think in square yards and plan seams around that roll width. Prices per square yard are typically higher than you would expect if you are used to per-square-foot pricing, so divide by 9 when comparing materials.
How much extra carpet should I buy for waste?
Plan on 10% extra for standard rectangular rooms with a straight carpet layout. Bump the waste allowance to 15-20% for rooms with lots of corners, doorways, and alcoves, for staircases, or when a patterned carpet must be matched at the seams. This calculator defaults to 10% waste and lets you type any percentage.
How do I measure an L-shaped room for carpet?
Split an L-shaped room into two rectangles on paper, measure the length and width of each rectangle in feet, and add the two square footages together. Add a room row for each rectangle in this calculator and it does the adding for you. This is more accurate than guessing one big rectangle, which over-counts the missing corner.
Does the waste allowance include seam matching for patterned carpet?
Not automatically. The 10% default covers cutting waste and odd room shapes, but patterned carpet needs extra material so the pattern lines up at every seam — installers often add 15-20% total for patterns. Type a higher waste percentage in the calculator when your carpet has a repeating pattern.