This carpet calculator finds the carpet and padding your room needs in square feet and square yards, plans around standard 12 ft roll width with waste, and prices the job.
| Room area | – |
| Carpet to buy (with waste) | – |
| Roll plan (12 ft roll) | – |
| Padding needed | – |
| Estimated carpet cost | – |
Carpet Sells by the Roll — Your Room Doesn't Care
Hard-surface floors (laminate, vinyl, hardwood by the box) are our Flooring Calculator. Part of our Construction Calculators collection.
Worked Example (Verified)
- 12 × 15 ft room (defaults): 180 sq ft = 20.0 sq yd; with 10% waste, buy 198 sq ft (22 sq yd) → carpet $891 at $4.50/sq ft. The room's 12 ft side matches a standard roll exactly, so one 15 ft cut covers it with no seams
- The seam tax: a 13 ft-wide room forces a second cut and a seam — waste jumps to 15–20% and the seam belongs away from traffic and light, two constraints that fight each other in most rooms
- Pattern repeat: patterned carpet must align its repeat (often 18–36″) across cuts — waste allowance climbs to 15%+ fast; solid colors forgive
Carpet Buying Discipline
- Pile direction must match across every cut in the room (light reflects differently) — the roll plan isn't just geometry, it's nap.
- Measure into closets and under door swings; measure twice at the room's widest points (walls wander).
- Pad is not optional comfort: it extends carpet life materially, and carpet warranties often require the specified pad density.
- Stairs price separately (per-step labor and wrapping) — no area formula survives contact with a staircase; get the installer's count.
Related Tools
- Flooring Calculator — boxes of hard flooring
- Paint Calculator — the walls above the carpet
- Construction Calculators — the full collection
Frequently Asked Questions
How do I calculate how much carpet I need?
Multiply room length × width for square feet, divide by 9 for square yards, then add 10% for waste (15–20% for patterns or seamed rooms). A 12×15 room: 180 sq ft = 20 sq yd, buy ≈ 22 sq yd. This calculator includes roll-width planning and pad.
Why does carpet come in 12 ft rolls?
Manufacturing standard: most residential broadloom is woven 12 ft wide (some 13 ft 2 in and 15 ft). Rooms narrower than the roll in one dimension need a single cut; wider rooms need seams. Planning cuts to minimize seam count — and hide the seams that remain — is the installer's craft.
How much extra carpet should I buy for waste?
10% for a simple solid-color room that fits the roll; 15% when seams or closets complicate; 20% for patterns with a large repeat. Leftovers aren't pure waste: keep a remnant for repairs and closet floors.
Does padding need the same amount?
Yes in area (order to the same with-waste square footage), though pad is cheaper and seams don't need matching. Specify pad by density (typically 6–8 lb) and thickness per the carpet maker's warranty — too-thick pad can void warranties and feel spongy.
How much does carpet installation cost?
Materials-plus-labor commonly lands $6–10 per sq ft all-in for mid-range carpet (carpet $3–5, pad $0.50–1, labor $1–2, plus removals and stairs itemized). The defaults' room runs ≈ $891 carpet-only at $4.50 — budget from the all-in band, not the carpet sticker.
Is this carpet calculator free?
Yes — free, instant, no sign-up.