Carpet Calculator
Square yards by the exact 9-foot law — with the twelve-foot roll and the per-yard price trap explained.
Carpet Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Rectangular rooms; stairs named as a chip, not modeled.
- One roll width (12 ft); 13.5/15 goods by hand.
- No install, tack strip or haul-away pricing.
In short: A 12 × 15 bedroom: 180 ft² = 20 yd² exact → 22 yd² ordered at 10% — $660.00 at $30/yd. Pad: $132.00. The 15-ft width crosses the 12-ft roll: one seam.
Formula
yd² = ft² ÷ 9 (exact)
order = ⌈yd² × (1 + waste)⌉
$30/yd² = $3.33/ft² — same carpet, 9× apart
rolls run 12 ft wide — seams where furniture lives
[('9', 'square feet per square yard — the whole law'), ('10/15/20%', 'plain / patterned / stairs waste chips'), ('12 ft', 'the roll’s width — seam doctrine'), ('pad', 'a second yard count, its own price')]
Worked Example
- Feet to yards by the exact 9 law.
- Waste by pattern and stairs; ceil the order.
- Check the 12-ft roll for seams.
- Price carpet and pad by the yard.
- Translate the yard quote back to feet before you sign.
The 12 × 15 bedroom: 180 ft² = 20 yd² exact → 22 ordered at 10% — $660.00 carpet + $132.00 pad at $30/$6. The $30 yard is $3.33 a foot; the roll seams once, under the bed.
Strengths & Limits Of This Model
Where this engine is strong
- The 9 law exact, the 9× trap on a card
- Seam doctrine tied to the real roll width
- Pad counted as its own yards
Where it stops
- Stairs approximated by chip
- No pattern-repeat layout mode
Practical Use Cases
Bedrooms
Yards to the exact nine.
Stairs
The 20% chip and a tacker’s patience.
Patterned loop
Seam matching priced before the install.
Pad orders
A second yard count, honest.
Store quotes
Yard-to-foot translation on demand.
Methodology & Editorial Standards
Square yards are the exact ft²÷9 law; the order ceils yards × (1 + waste chip). The 12-ft roll governs a seam card when the room crosses it. Cost is carpet plus pad at free-entry per-yard quotes, and the per-foot translation is printed to kill the 9× confusion. Zero rooms are refused.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Carpet Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many square yards of carpet for a 12x15 room?
180 ft² ÷ 9 = 20 yd² exact; 22 ordered at 10% waste. At $30 a yard: $660 carpet, $132 pad — the sourced worked example.
How do I convert square feet to square yards?
Divide by 9 — a square yard is three feet by three feet. The law is exact, so 198 ft² is 22 yd², no rounding mystique.
Why do stores quote carpet per square yard?
Trade history — the yard was the industry’s unit long before big-box foot pricing arrived. Both numbers describe the same roll; always translate one into the other before comparing stores.
What is carpet roll width?
Twelve feet standard, with 13.5- and 15-ft goods in some lines. Rooms wider than the roll seam — plan the seam away from walkways and toward furniture.
How much waste should carpet carry?
10% plain, 15% patterned (the match eats it), 20% on stairs and angled rooms. closets and doorways ride the same chip.
Does carpet padding matter?
It is half the feel and half the wear — rebond pad at 6-8 lb is the residential default; thick and soft is not better, it wrinkles. Budget the pad as its own yard count.
How long does carpet last?
Ten to fifteen years of honest traffic for mid-grade nylon and polyester; loops and wool longer. Traffic lanes age first — color hides wear, texture shows it.
Can I install carpet myself?
One room with a knee kicker, maybe; a seam, stretch and trim job is a tool-rental education. The yard count here works either way — the installer will quote the same number.
Is carpet priced by installation included?
Rarely — the per-yard quote is material; padding, install, tack strip and haul-away are lines. Ask for the all-in per-yard figure before comparing stores.
How do stairs count?
Roughly one yard per 10-13 steps depending on width and nosing, with the 20% chip for cuts — and a runner down the middle changes the math entirely. Measure tread plus riser, count twice.