Measuring & waste
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.
Four units for one floor
A floor is measured in square feet, but the products that cover it are priced and sold in at least four ways. Tile, wood, laminate and vinyl are priced per square foot and sold by the box or carton. Carpet is priced per square yard in the US and sold by the linear foot of roll. Products made for Europe and Canada are often labelled in square metres. And every quote rolls them up into one total. Mixing them up is how a carpet quote looks cheaper than it is, or a box count comes out a fifth wrong.
The exact conversions
The foot has been exactly 0.3048 metres since 1959, so every area conversion is exact and can be done in either direction without drift.
| From | To | Multiply by | Example |
|---|---|---|---|
| square feet | square yards | ÷ 9 | 180 sq ft = 20 sq yd |
| square yards | square feet | × 9 | 20 sq yd = 180 sq ft |
| square feet | square metres | × 0.09290304 | 180 sq ft = 16.72 m² |
| square metres | square feet | × 10.7639 | 10 m² = 107.64 sq ft |
| square feet | square inches | × 144 | 1 sq ft = 144 sq in |
A square yard is 3 ft × 3 ft, which is 9 square feet, not 3. That single slip, dividing by 3 instead of 9, triples a carpet quote on paper.
Prices: always compare per square foot
A carpet at $27 per square yard is $3 per square foot. A tile at €40 per square metre is €3.72 per square foot. To compare, convert every price to the same unit first.
The last line matters most for boxed flooring. Two vinyl planks at $55 a box look the same until you read that one box covers 23.6 sq ft and the other 18.9: $2.33 against $2.91 per square foot.
Boxes and cartons
Boxed flooring is labelled with its coverage: square feet per box, and often the pieces per box. To turn an area into boxes, add the waste, divide by the coverage and round up once. Typical coverages by material are on the coverage per box reference.
What 14 leftover boxes cover
14 boxes of vinyl plank at 23.6 sq ft per box.
- 14 × 23.6 = 330.4 sq ft, 36.71 sq yd, 30.7 m²
Enough for a 300 sq ft room with 10% waste. Leftover boxes from one project are worth checking against the next, provided they share a lot number.
The boxes and cartons calculator does the box arithmetic with waste, spare and tax; the flooring unit converter turns any area into boxes and back.
Rolls: linear feet, not area
Carpet and sheet vinyl are cut from rolls of fixed width, usually 12 ft. You buy a length of roll, and the area is that length times the width. A linear foot of 12 ft carpet is 12 square feet, or 1.33 square yards. Because the width is fixed, the area you buy is often much larger than the room.
A carpet quote checked
A 14 × 13 ft bedroom is 182 sq ft, or 20.2 sq yd. On a 12 ft roll it needs two strips 13.5 ft long, which is 27 ft of roll, 324 sq ft, 36 sq yd.
At $32 per square yard, a quote for 20.2 sq yd ($646) is impossible from a 12 ft roll; the real figure is 36 sq yd ($1,152). A 13.5 ft roll would do it in one piece of 21.8 sq yd.
The carpet calculator works out the strips, and the guide to carpet roll arithmetic explains why 12 ft matters so much.
Square metres on a US product
Some products sold in the US are made for international markets and print the coverage in square metres, sometimes with a square-foot figure rounded differently. Use the figure the maker gives in your unit if there is one; if not, convert with 10.764. A box labelled 2.2 m² covers 23.7 sq ft.
Trim and other linear products
Not everything on a flooring order is sold by area. Baseboard, shoe moulding, quarter round, T-mouldings and reducers are sold by the piece, usually 8 ft long for wood trim and 7 to 8 ft for transitions. Carpet tack strip comes in 4 ft pieces. These follow the length of the walls and doorways, not the area, so they need the perimeter, not the square feet. A 250 sq ft room can have 60 ft of wall or 80 ft depending on its shape, and the difference is three pieces of every trim you buy.
Thicknesses are the last unit to watch. Plank and tile thickness is given in millimetres on most labels, even in the US, while underlayment and subfloor are given in fractions of an inch. A 6 mm vinyl plank on a 1 mm pad is about 0.28 inches in all, which is what decides whether a door clears and which transition strip fits.
Quotes
A quote may give the area, the price per square foot or square yard, and a total. Check that the area matches your measurement of the floor, not the floor plus waste; that the unit is what you think; and that the total equals area times price plus anything listed separately. The complete method covers measuring, and the guide to measuring odd rooms covers the rooms where measurements most often go wrong.
The short version
Nine square feet to a square yard, 10.764 to a square metre. Compare prices per square foot. Divide a box price by its coverage. Buy carpet and sheet vinyl by length of roll, and expect the area bought to exceed the room.