★ CONSTRUCTION · FLOORING
A 12 × 10 ft room costs $871.20 to carpet. The room is 120 sq ft, but you buy 132 sq ft once waste is added: $594.00 of carpet, $79.20 of padding and $198.00 of installation. Enter your room size and prices to cost any room, or work out the biggest room a budget buys.
Carpet is priced by the square foot, but a room never takes exactly its own area: the roll is 12 feet wide, the pattern has to match, and the cuts around doorways and closets leave offcuts. Installers add a waste allowance — usually 10% — and charge for carpet, padding and fitting separately. This calculator multiplies the room out, adds the waste, and prices each part so the quote you get has nowhere to hide.
Carpet is sold by the square foot, but the number you pay for is not the room’s area — it is the room’s area plus a waste allowance. The roll comes 12 feet wide, so a room that is 10 feet wide leaves a 2-foot strip, the pattern has to line up across seams, and the cuts around doorways and closets leave pieces too small to use. Installers add 10% for a plain carpet in a square room, and 15% for a patterned carpet or an awkward room. Every part — carpet, padding and fitting — is priced on the same billable area, so the total is the billable area times the three rates added together.
At the defaults — a 12 × 10 ft room, 10% waste, carpet $4.50/sq ft, padding $0.60/sq ft, install $1.50/sq ft — the room is 12 × 10 = 120 sq ft (13.33 sq yd), and the billable area is 120 × 1.10 = 132 sq ft (14.67 sq yd). The carpet costs 132 × $4.50 = $594.00, the padding 132 × $0.60 = $79.20, and the fitting 132 × $1.50 = $198.00, for a total of $871.20 — which is $871.20 ÷ 120 = $7.26 per square foot of room.
| Room | Area | Billable (10% waste) | Carpet | Padding | Install | Total |
|---|---|---|---|---|---|---|
| 12 × 10 ft (default) | 120 sq ft | 132 sq ft | $594.00 | $79.20 | $198.00 | $871.20 |
| 15 × 12 ft | 180 sq ft | 198 sq ft | $891.00 | $118.80 | $297.00 | $1,306.80 |
| 12 × 10 ft, carpet $6.00 | 120 sq ft | 132 sq ft | $792.00 | $79.20 | $198.00 | $1,069.20 |
| 12 × 10 ft, waste 15% | 120 sq ft | 138 sq ft | $621.00 | $82.80 | $207.00 | $910.80 |
| 12 × 10 ft, no padding charge | 120 sq ft | 132 sq ft | $594.00 | $0.00 | $198.00 | $792.00 |
Setup: a 12 × 10 ft room, 10% waste, carpet $4.50/sq ft, padding $0.60/sq ft, install $1.50/sq ft.
Line 1 — the room area. 12 × 10 = 120 sq ft, which is 120 ÷ 9 = 13.33 sq yd (a square yard is 9 square feet).
Line 2 — the billable area. 120 × 1.10 = 132 sq ft (14.67 sq yd). The 10% waste adds 12 sq ft.
Line 3 — the carpet. 132 × $4.50 = $594.00.
Line 4 — the padding. 132 × $0.60 = $79.20.
Line 5 — the installation. 132 × $1.50 = $198.00.
Line 6 — the total. $594.00 + $79.20 + $198.00 = $871.20, or $871.20 ÷ 120 = $7.26 per square foot of room.
Line 7 — the budget check. The three rates add to $4.50 + $0.60 + $1.50 = $6.60 a sq ft, so $1,000 buys $1,000 ÷ $6.60 = 151.52 sq ft of carpet, which covers a 151.52 ÷ 1.10 = 137.74 sq ft room after waste.
15 × 12 ft room: the area is 15 × 12 = 180 sq ft and the billable area is 180 × 1.10 = 198 sq ft, so the total is 198 × $6.60 = $1,306.80. A room half as big again costs half as much again — carpet cost scales with area, so doubling the room doubles the bill.
Carpet at $6.00/sq ft: the carpet alone costs 132 × $6.00 = $792.00, and the total rises to $1,069.20. The upgrade from $4.50 to $6.00 carpet adds $198 to this room — the price difference is multiplied by the billable area, not the room area, so waste makes upgrades dearer than they look.
Waste 15%: the billable area rises to 120 × 1.15 = 138 sq ft and the total to $910.80. Five extra points of waste add 6 sq ft, or $39.60 — patterned carpet and awkward rooms are genuinely dearer, not just harder to fit.
No padding charge: with the padding at $0, the total falls to $792.00 — the $79.20 of padding disappears. If a quote says padding is included, enter $0 here rather than paying for it twice; if the quote charges for it separately, leave the $0.60 in.
Reverse — the $1,000 budget: the three rates add to $6.60 a sq ft, so $1,000 ÷ $6.60 = 151.52 sq ft of carpet. Divide by the 1.10 waste factor and the biggest room it covers is 137.74 sq ft — about a 12 × 11.5 ft room. A 12 × 12 ft room (144 sq ft) needs 158.4 billable sq ft, or $1,045.44, so it is just over budget.
The model assumes a rectangular room: L-shaped rooms, bay windows and built-in wardrobes change the waste, because the carpet has to be cut around them. It assumes the carpet is bought by the square foot at a flat rate — in reality carpet is often sold by the square yard (9 sq ft) or by the linear foot off a 12-foot roll, and a room narrower than 12 feet still pays for the full roll width in places. It leaves out removal of the old carpet, moving furniture, stair treads (which are priced by the step, not the square foot), transitions between rooms, and tax. The 10% waste is the industry standard for plain carpet in a square room; patterned carpet needs 15% or more, and a room with a lot of doorways can need more still. Rounding convention: money is rounded to cents and all figures are computed from unrounded values, rounded only for display.
| Output | Formula | What it means |
|---|---|---|
| Room area | length × width | 120 sq ft (13.33 sq yd). |
| Billable area | area × (1 + waste) | 132 sq ft (14.67 sq yd). |
| Carpet material | billable × carpet $/sq ft | $594.00. |
| Padding | billable × padding $/sq ft | $79.20. |
| Installation | billable × install $/sq ft | $198.00. |
| Total cost | carpet + padding + install | $871.20. |
| Cost per room sq ft | total ÷ room area | $7.26. |
| 15 × 12 ft room | same model, 15 × 12 ft | 180 sq ft, 198 billable, total $1,306.80. |
| Carpet $6.00 | same model, carpet $6.00 | Material $792.00, total $1,069.20. |
| Waste 15% | same model, waste 15% | 138 sq ft billable, total $910.80. |
| No padding charge | same model, padding $0 | Total $792.00. |
| Reverse: $1,000 budget | $1,000 ÷ combined rate; ÷ (1 + waste) | 151.52 sq ft of carpet, 137.74 sq ft room. |
The math is exact for the numbers you enter: the room area is length times width, the billable area is the room area times one plus the waste, and each cost is the billable area times its rate. What the model cannot do is measure your room for you: measure wall to wall at the longest points, and for an L-shaped room split it into two rectangles and add them. It leaves out old-carpet removal, furniture moving, stair treads, transitions, and tax — ask the installer whether the quote includes those, and add them yourself if it does not. It assumes carpet is priced by the square foot; if your shop prices by the square yard, divide the per-yard price by 9. The waste allowance is an estimate: a plain carpet in a square room is 10%, a patterned carpet or an awkward room is 15% or more, and a room with a lot of doorways can need more still. For flooring in general, see tile size chart; for the room itself, see paint coverage chart.
Bright Side Kit. "Carpet Cost Calculator: Price Per Room & Install 2026." https://brightoolbox.com/carpet-cost-calculator/ Accessed October 24, 2026.$871.20. The room is 120 sq ft, but you buy 132 sq ft once the 10% waste allowance is added: $594.00 of carpet, $79.20 of padding and $198.00 of installation, at $4.50, $0.60 and $1.50 a square foot.
132 sq ft, or 14.67 sq yd. The room is 120 sq ft, and the 10% waste allowance adds 12 sq ft for cuts, pattern matching and offcuts. Carpet is often sold by the square yard, so divide by 9: 132 ÷ 9 = 14.67 sq yd.
10% for a plain carpet in a square room, 15% for patterned carpet or an awkward room. The roll is 12 feet wide, the pattern has to line up across seams, and the cuts around doorways leave pieces too small to use. At 15% waste this room needs 138 sq ft and costs $910.80.
About $1 to $2 a square foot. The defaults use $1.50, which is $198.00 on this room. Stairs cost more — they are priced by the step, not the square foot — and removal of old carpet and furniture moving are usually charged separately.
About $0.50 to $0.70 a square foot. The defaults use $0.60, which is $79.20 on this room. If a quote says padding is included, enter $0 for padding here rather than paying for it twice; with no padding charge this room costs $792.00.
A 137.74 sq ft room. The three rates add to $6.60 a square foot, so $1,000 buys 151.52 sq ft of carpet, and after the 10% waste that covers a 137.74 sq ft room — about 12 × 11.5 ft. A 12 × 12 ft room needs $1,045.44, so it is just over budget.
Both, depending on the shop. This calculator uses square feet, because that is how most online prices are shown. A square yard is 9 square feet, so a $40.50-per-yard carpet is $4.50 a square foot. This room is 120 sq ft, or 13.33 sq yd, and needs 14.67 sq yd with waste.
Because of waste. The 10% waste allowance adds 12 sq ft to this room, or $79.20 at the combined $6.60-a-square-foot rate. The roll is 12 feet wide, the pattern must match, and the cuts around doorways leave offcuts — none of that carpet is usable, but all of it is bought.