Flooring Calculator
Flooring = floor area × 1.10 (× 1.15 laid diagonally) ÷ the coverage of one box. A 12 × 15 ft room is 180 ft²: 198 ft² to order, 10 boxes at 20 ft² each. The 20 ft² box is only an example: type the coverage printed on your carton, it changes with every product.
Boxes to buy
10 boxes
198 ft² with 10 % extra, boxes of 20 ft²
- Floor area
- 180 ft² (16.72 m²)
- Boxes without the extra
- 9
- Left over after the job
- 2 ft²
Shaw asks you to lay from several cartons at a time so color and shade mix; keep the leftover planks for later repairs.
Worked examples
A 12 × 15 ft room, straight layout, boxes of 20 ft²
- 12 × 15 = 180 ft²
- 180 × 1.10 = 198 ft²
- 198 ÷ 20 = 9.9, so 10 boxes
Result: 10 boxes (200 ft²), 2 ft² left over.
Checked by the automated test “flooring — 12 × 15 ft room, 10 % extra, boxes of 20 ft² → 198 ft² to order, 10 boxes”.
The same room laid diagonally
- 180 × 1.15 = 207 ft²
- 207 ÷ 20 = 10.35, so 11 boxes
Result: 11 boxes of 20 ft².
Checked by the automated test “flooring — the same room laid diagonally: 15 % → 207 ft², 11 boxes”.
How it works
Floor area = Σ length × width of each room
To order = floor area × (1 + extra %)
Boxes = to order ÷ coverage of one box, rounded up
Assumptions
- Extra: 10 % for a straight layout, the top of the 5-10 % that Shaw and Tarkett ask for; 15 % on a diagonal (Tarkett). Shaw says herringbone and bordered floors need more without giving a figure, so the calculator asks you to type it.
- Box coverage is read on the carton: it changes with every product, and 20 ft² is only an example.
- Rooms are rectangles; split an L-shaped room into two.
Reference table
| Floor area | 5 % extra | 10 % extra (straight) | 15 % extra (diagonal) |
|---|---|---|---|
| 100 ft² | 105 ft² | 110 ft² | 115 ft² |
| 150 ft² | 157.5 ft² | 165 ft² | 172.5 ft² |
| 200 ft² | 210 ft² | 220 ft² | 230 ft² |
| 300 ft² | 315 ft² | 330 ft² | 345 ft² |
| 500 ft² | 525 ft² | 550 ft² | 575 ft² |
Divide by the coverage on the carton and round up to get the boxes.
Before you buy
- Several rooms. Add each room as its own line; the extra is applied once, to the total.
- Box coverage. Read the ft² per box on the carton or the product page, not the plank size.
Common mistakes
- Ordering the floor area alone Shaw and Tarkett both add 5 to 10 % for cuts: a 180 ft² room needs 198 ft² of flooring, not 180.
- The same extra on a diagonal Tarkett raises the extra to 15 % on a diagonal: 207 ft² for the same 12 × 15 ft room, 11 boxes instead of 10.
- Rounding boxes to the nearest Boxes are bought whole and rounded up: 9.9 boxes is 10, never 9.
- Keeping nothing for repairs Tarkett's extra also leaves planks for a future repair: keep them instead of returning the last box.
- Laying one carton at a time Shaw asks you to work out of several cartons at a time so the color and shade mix across the floor.
Frequently asked questions
How much flooring do I need?
Multiply length by width for each room, add the rooms, then add 10 % for a straight layout or 15 % on the diagonal. A 12 × 15 ft room is 180 ft²: order 198 ft², or 207 ft² laid diagonally.
How much extra flooring should I buy?
Shaw and Tarkett ask for 5 to 10 % on a straight layout and Tarkett 15 % on a diagonal; Shaw says herringbone and bordered floors need more. The calculator uses 10 % and 15 %; keep the leftover planks, Tarkett's extra also covers a future repair.
How many boxes of flooring do I need?
Divide the area to order by the coverage printed on the box and round up: 198 ft² in boxes of 20 ft² is 9.9, so 10 boxes; in boxes of 23.5 ft² it is 8.4, so 9 boxes.
How do I measure square feet for flooring?
Measure each room wall to wall in feet and multiply length by width; split an L-shaped room into rectangles. A 12 × 15 ft room plus a 5 × 8 ft hall is 220 ft².
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- Solid hardwood installation instructions (5-10 % waste factor, depending on layout) — Shaw Hardwood Flooring, accessed
- Laminate installation instructions, all collections (5-10 % straight, 15 % diagonal) — Tarkett, accessed