Tools and tables

Quantity calculator: area, overage and boxes

Enter up to four areas and anything to subtract, an overage and the coverage on one box. Get the net area, the area with overage, whole boxes to order and what is left over. Lengths in feet and inches or in meters.

Units Area 1 length (12' 6", 12 6 or 12.5; metric: 3.8 or 380 cm) Area 1 width Area 2 length (blank to skip) Area 2 width Area 3 length (blank to skip) Area 3 width Area 4 length (blank to skip) Area 4 width To subtract (an island, a hearth): length To subtract: width Overage (%) Coverage per box (sq ft, or m² in metric) Spare boxes to keep

Assumptions behind the numbers

Area is length times width for each rectangle, added up, minus the area to subtract. Split an L-shaped room into two rectangles. Measure to the wall, not to the baseboard, and round each length up to the next inch or centimeter.
Lengths in feet and inches: 12' 6", 12 ft 6 in, 12 6 and 12.5 all mean twelve and a half feet; a number ending in " or in is inches only. Metric lengths are meters, or centimeters when they end in cm. One square foot is 0.09290304 square meters.
Overage covers cutting waste and boards or tiles graded out. The default of 10 percent is this manual's convention where a maker gives no figure. Bruce's instructions for its solid hardwood say 5 percent, 10 percent for diagonal installations and 10 to 15 percent for glue-down. Other materials follow their own maker's instructions.
Boxes are rounded up to whole boxes after overage, then the spares are added. Buy every box from one lot (the run or batch printed on the box) and write the lot on your installed register: color can differ from lot to lot.
Carpet comes in rolls, usually 12 ft wide (CRI's Carpet Primer), and the installer plans seams and the direction of the pile. For carpet this calculator gives area only; the order comes from the installer's seam plan.

Fictional example

The Brennans' kitchen is 12 ft by 14 ft, less a 3 ft by 6 ft island: 168 less 18 is 150 sq ft. With 10 percent overage that is 165 sq ft. At 23.4 sq ft a box, 165 needs 8 boxes (187.2 sq ft), and they keep 1 spare, so they order 9 from one lot. Enter 12, 14, 3, 6, 10 percent, 23.4 and 1 above to see the same figures. The family and their kitchen are invented for this manual.

Limits

The calculator multiplies what you measure. It does not see a room that is out of square, a pattern that wastes more, a stair, or a seam plan, and it does not replace the installer's own count. Use the maker's overage where the instructions give one, and ask the installer to confirm the order before you buy.