Calculators
Carpet calculators
Broadloom from the roll, carpet tiles, padding, tack strip, stairs and the right size of rug.
Carpet is the one flooring where the room's shape matters more than its area. Broadloom comes off a roll 12 feet wide (13.5 and 15 feet for some products), so a room is covered by one or more strips of that width running the full length, and the question is not how many square feet you need but how many linear feet of roll, with how many seams, running which way. A 10 × 12 ft bedroom takes 10 ft of roll and no seam; a 13 × 14 ft one takes two strips and a seam, and nearly a third of the second strip is waste.
The calculators here plan that cut. The carpet calculator picks the better roll direction and counts seams; the seam planner shows every option side by side; the padding, tack strip and stair tools finish the shopping list. Carpet tiles are the exception, bought by the box like any tile, and the rug calculator answers the question that comes before any of this: which standard size fits the furniture.
7 calculators
Carpet Calculator
The length of 12, 13.5 or 15 ft roll a room takes, the seams, the square yards and the cost.
Carpet Tile Calculator
Carpet tiles and boxes by size and installation pattern, with the adhesive tabs or tackifier.
Carpet Padding Calculator
Rolls and square yards of carpet pad by type and density, with the seam tape and staples.
Tack Strip Calculator
Tack strip pieces and bundles from the room perimeter less the doorways, for wood or concrete.
Stair Carpet Calculator
Carpet or runner for a flight of stairs from the steps, treads and risers, with landings and pad.
Rug Size Calculator
The standard rug size that fits your furniture and still leaves floor showing at the walls.
Carpet Seam Planner
Both ways to lay a carpet roll across a room, with the seams, the light and the offcut compared.
Guides for this topic
Carpet padding: density, thickness and how much to buy
The pad decides how a carpet feels and how long it lasts. Density matters more than thickness, and the carpet's warranty usually tells you the minimum of both.
Carpet roll math: why a 13 ft room costs so much more than a 12 ft one
Carpet is bought by the length of a roll 12 ft wide. A room up to 12 ft wide in one direction takes one piece. A room an inch wider takes two, and pays for a whole second strip.
Carpeting stairs: full-width carpet or a runner, and how much
Stair carpet is counted by the step, not by the area. Each step takes the tread, the riser and the nosing, and a flight of fourteen is about 22 ft of carpet before landings.
Measuring L-shaped, angled and odd rooms for flooring
Any room can be measured as rectangles that do not overlap. Here is how to split the awkward ones, what to include and leave out, and why an L-shape has the same perimeter as a plain rectangle.
Rug size rules for living rooms, dining rooms and bedrooms
A rug is sized by the furniture on it, not by the room. Too small is the common mistake. Here are the rules for each room and the standard sizes they lead to.
Sheet vinyl: roll widths, seams, pattern match and how much to buy
Sheet vinyl comes in rolls 6, 12 or 13.2 ft wide, and you buy a length. A room that fits the roll needs no seam and wastes little; a room just over it can waste 40%.
Square feet, square yards and boxes: the units of flooring
Tile is priced per square foot, carpet per square yard, European products per square metre, and you buy all of them by the box or the roll. Here are the exact conversions and the traps between them.
Underlayment: which type, how many rolls, and when you need none
Underlayment smooths small flaws, softens footfall, cuts noise and keeps slab moisture out. The right one depends on the floor above and the subfloor below, and sometimes the right one is none.
Questions people ask
- How much carpet for a 12 × 15 foot room?
- Run a 12 ft roll along the 15 ft length and the room takes a single strip 15 ft long: 180 sq ft, 20 sq yd, no seam, nothing wasted but the trimming. Turn it the other way and you need two strips of 12 ft with a seam and 108 sq ft of offcut. The calculator picks the first option and tells you why.
- Why is carpet priced per square yard?
- Habit from the roll trade: a 12 ft roll is 4 yards wide, so one linear yard of roll is 4 square yards, and the industry never changed. One square yard is 9 square feet. A price of $27 per sq yd is $3 per sq ft; the unit converter does both directions.
- What density of carpet padding should I buy?
- The Carpet and Rug Institute's minimum for residential cut-pile carpet is 6 lb per cubic foot density at 7/16 inch thick or less; 8 lb is the usual choice for stairs and halls and for most manufacturer warranties. Thicker is not better: pad over 7/16 inch lets the carpet flex and the seams open.
- How much carpet do stairs take?
- Each straight step takes about 20 inches of carpet along its depth (a 10 inch tread plus a 7 to 8 inch riser plus the nosing), so 13 steps need roughly 22 ft of length. A full-width stair uses a strip the width of the stairs plus 3 inches each side to tuck; a runner uses its own width. Winders and landings are measured separately.
- What size rug goes under a sofa?
- The front legs of the sofa and chairs should sit on the rug, with the rug extending at least 6 to 8 inches beyond the sofa at each end. For a standard 84 inch sofa facing two chairs that is usually an 8 × 10 ft rug; a 9 × 12 ft lets every leg of every piece sit on it. The rug size calculator applies the rule to your layout.
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