Carpet Calculator

How much carpet do you actually need? This free carpet calculator gives DIYers and flooring contractors a complete materials list — broadloom square yards with roll-width seam plan, carpet pad rolls (6' × 45' = 270 sq ft), tackless gripper strip in 4 ft pieces, hot-melt seam tape, seam sealer, Z-bar and binder-bar transitions, and an optional waterfall or Hollywood stair runner.

Every other free carpet calculator online stops at "area × 1.1 ÷ 9 = square yards." That ignores the part installers actually plan around: carpet does not bend. If your room is wider than the roll, you need a fill piece seamed in — and the seam adds material AND a labor step AND a CRI 105 placement constraint. Berber and patterned goods change the math again with pad-class restrictions and pattern-repeat allowances.

Built on the Carpet & Rug Institute installation standards (CRI 104 commercial, CRI 105 residential), HUD/FHA UM 72a cushion classes via the Carpet Cushion Council, ASTM D5252/D5417 durability tests, ASTM F1869/F2170 subfloor moisture limits for glue-down, and CRI Green Label Plus VOC certification. Materials only — no pricing, no labor, no signup.

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Carpet Calculator

Estimate broadloom carpet (with seam plan), pad, tackless strip, seaming tape, transitions, and stair runner — per CRI 104/105 and HUD UM 72a.

Rooms

Note: All rooms below share the same carpet, fiber, roll width, pad, and install method. For different carpets in different rooms (e.g. Berber in bedrooms, plush in the living room), run the calculator separately for each spec.
ft
ft
count
in
count

Doorways subtract from tackless-strip LF. The carpet→carpet count drives Z-bar transitions vs binder bars.

Carpet selection

in

Set repeat to 0 for solid or random-texture carpet. Patterned goods add one repeat of length per seam (per CRI 105 / FlooringInc pattern-match guide).

Pad / cushion

Berber and commercial loop carpets require Class 2 cushion ≤3/8". Using a thicker / softer pad voids most wear warranties — the calculator will warn you.

Installation method

Triggers ASTM F1869 / F2170 moisture-test note when paired with glue-down.

Stairs (optional)

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How to Use This Calculator

  1. Add every room you're carpeting: enter length and width in feet. Add doorways (count and width in inches) for tackless and transition math.
  2. Pick carpet construction: cut pile (plush, Saxony, frieze), loop (level loop, Berber), cut-and-loop / patterned, or commercial broadloom. Construction drives base waste % (10% solid cut pile, 15% Berber and patterned) and pad-class compatibility.
  3. Pick fiber: nylon for high traffic, triexta for pets and basements, polyester for soft / budget, olefin for moisture-prone areas, wool for premium.
  4. Pick broadloom roll width: 12 ft is the US residential standard, 15 ft eliminates seams in 12–15 ft rooms, 13'2" is the European / wool standard, 6 ft is utility / commercial.
  5. Enter pattern repeat in inches if the carpet is patterned (0 for solid). Each seam after the first needs one repeat of length added.
  6. Pick pad: 8 lb / 7/16" rebond is the residential default. Berber and commercial loop need Class 2 (10 lb rebond ≤ 3/8" or synthetic fiber). The calculator warns when carpet and pad are mismatched.
  7. Pick install method: stretch-in over pad (residential standard), direct glue-down (commercial), or double-glue. Check "concrete subfloor" to surface the ASTM F1869 / F2170 moisture-test note for glue-down installs.
  8. Optional — add stairs: enter step count, tread depth, riser height, runner width, and pick waterfall (drapes over the nose) or Hollywood (wraps tight). Defaults match IRC R311.7 stair dimensions.
  9. Click Calculate: see square feet and square yards to order with the waste factor included, per-room broadloom layout with seam plan, pad rolls, tackless pieces, seam tape rolls, transitions, and an installation-notes block with dye-lot and acclimation guidance.

Why Roll-Width Geometry Matters More Than Waste Percentage

Carpet is sold by the linear foot of full roll width — not by net square footage. A 12 ft × 14 ft bedroom on 12 ft broadloom is seamless: one strip 14 ft long × 12 ft wide = 168 sq ft. But a 14 ft × 12 ft bedroom (same room, rotated) becomes 14 ft wide × 12 ft long — and 14 ft exceeds the 12 ft roll. Now you need two strips (12 ft + 2 ft fill piece), one seam 12 ft long, and roughly 192 sq ft of face material instead of 168. Same room, +14% material, plus a seam. The calculator orients strips along the longer side automatically to minimize seams, then applies the construction-specific waste % on top of the roll-width geometry. That is the materials list your supplier will quote against — not the bare floor area. CRI 105 §10 ("Seams") and §11 ("Stretch-in Installation") govern seam placement and the long-run rule: stretched walls over 30 ft require architectural-grade tackless or two parallel strips, because a single strip will not hold a power-stretcher tension over that distance.

Frequently Asked Questions

How much carpet do I need for a 12×14 bedroom?

12 ft × 14 ft = 168 sq ft net floor area. On 12 ft broadloom, run the carpet length along the 14 ft side — one strip, no seam, 14 ft running × 12 ft roll width = 168 sq ft of face material. Add 10% waste for cuts and dye-lot reserves: 184.8 sq ft ÷ 9 = 20.5 square yards to order. If the room were 14 ft × 12 ft instead (same room, rotated relative to the roll), the 14 ft dimension would cross the roll width — now you need two strips with a 12 ft seam and roughly 192 sq ft of face. Same room, +14% material. This is why every carpet calc that ignores roll width under-orders.

What's the standard carpet waste factor?

Per CRI 105 commentary and installer practice: 10% for solid cut pile (plush, Saxony, frieze) in simple rectangular rooms — this is the near-universal residential default. 15% for loop pile (level loop, Berber, commercial) and for any patterned carpet because seams must align. 20%+ for complex rooms (L-shapes, multi-closet, irregular). For patterned broadloom, ADD a pattern-repeat allowance on top: one full repeat of length per cut after the first. A 24-inch pattern × 3 seams = 6 extra feet of running length.

What size carpet pad do I need?

Per HUD UM 72a (Carpet Cushion Council): bonded rebond urethane at 8 lb/ft³ density and 7/16" thickness is the residential standard for cut-pile carpet (Class 1 cushion). 6 lb is budget; 10 lb is high traffic. Berber, level loop, and commercial broadloom require Class 2 cushion — denser AND thinner: 10 lb rebond ≤3/8" or synthetic fiber pad. Pad thicker than 3/8" under Berber causes loop flex and seam separation, voiding most manufacturer warranties. Pad rolls are 6 ft × 45 ft = 270 sq ft. Round up: net floor area × 1.05 ÷ 270 = pad rolls needed.

How many feet of tackless strip do I need?

Tackless strip linear feet = room perimeter minus doorway widths. A 12 × 14 ft room with one 36-inch doorway: perimeter is 2 × (12 + 14) = 52 LF, minus 3 ft for the doorway = 49 LF. Strip is sold in approximately 4 ft pieces: 49 ÷ 4 = 13 pieces. Per CRI 105, the gully (gap between strip and wall) must be slightly less than carpet thickness and never exceeds 3/8". For stretched runs over 30 ft, CRI 105 requires architectural-grade strip (1-3/4" wide, 3 rows of pins) or two parallel conventional strips — single strip will not hold the power-stretcher tension.

Waterfall vs Hollywood stair carpet — what's the difference?

Waterfall installation drapes the carpet over the tread nose and straight down to the next tread (not fastened to the riser face). It's faster, uses less material, tolerates thick or patterned goods, and is the most common residential method. Hollywood (cap-and-band, upholstered) wraps the carpet tightly around each nose and tucks/staples it to both tread and riser — more material and labor but produces a tailored look with a crisp nose. Best with low-to-medium pile in formal stair halls. Per-step run: waterfall ≈ (tread + riser + 2") ÷ 12; Hollywood adds about 3 more inches per step for the wrap. Add 10% per CRI / runrug practice.

Do I need a moisture test before glue-down carpet?

Yes — CRI 105 requires it on any concrete subfloor for glue-down or double-glue installation, and skipping it is the #1 failure mode for glue-down carpet. Two acceptable tests: ASTM F1869 calcium chloride MVER must read ≤ 3 lb per 1000 sq ft per 24 hr, or ASTM F2170 in-situ relative humidity probes must read ≤ 75% RH. F2170 needs 3 probes for the first 1,000 sq ft + 1 per additional 1,000 sq ft, with the slab conditioned at service temperature and humidity ≥ 48 hr before reading. The full procedure is documented in ASTM F2170-23. Failed tests mean either a vapor barrier or a delay until the slab dries — not a glue-down install.

How is carpet priced — by square foot or square yard?

Carpet has historically been priced per square YARD in the US, though many retailers (Lowe's, Home Depot, Empire Today) now quote per square FOOT to match how flooring is sold. The unit your supplier quotes is the LINEAR FOOT OF FULL ROLL WIDTH — they cut from a 12 ft or 15 ft roll and bill the running length × the roll width. The calculator reports both: square feet to order (the literal supplier line item) and square yards (legacy convention; divide sq ft by 9). Always confirm with the supplier whether their per-square-foot quote is on the running length × roll width or on your bare room area — the difference is the seam math the calculator handles.

Why do I need to match dye lots?

Every carpet production run produces a slightly different shade — the dye lot or batch number. Different lots installed side-by-side or as a spot repair show as visible color bands under raking light, even when the SKU is identical. Always order all carpet for one contiguous area in a single purchase order from a single dye lot, confirm the lot number on the invoice, and again on the rolls when delivered. Order a 5–10 sq yd attic-stock piece for future repairs — pet stains, burns, and seam openings need a dye-lot match years later, and reorder lots are rarely available. Stairs should share a dye lot with the adjacent room or landing — ordering them as a separate after-the-fact purchase virtually guarantees a mismatch.