Measuring & waste
How much flooring do I need? The complete method
Measure the room in rectangles, add the waste your layout demands, divide by what the box really covers, round up once, and count the trim. Here is each step, with a living room worked from start to finish.
The method in one paragraph
Every flooring order is the same five steps. Measure the floor area as the room really is, in rectangles. Choose the waste allowance for your material and layout. Multiply the area by one plus the waste. Divide by the coverage printed on the box, carton or roll, and round up once. Then measure the walls for the trim. The order of the steps matters: rounding too early, adding waste twice, or using a coverage you assumed instead of read are the three mistakes behind most short and over-ordered floors.
Step 1: measure the area as rectangles
Rooms are rarely one rectangle. Split the room at its inside corners into rectangles that do not overlap, measure each at its longest and widest points wall to wall, and add them. Include closets, the floor under door swings and the threshold to the middle of the door. Subtract only what the new floor will stop at: a raised hearth, an island set on the subfloor, a built-in cabinet. Freestanding furniture and appliances do not come off; the floor goes under them.
Measure each dimension at both ends of the wall and use the larger figure. Walls are rarely parallel, and the floor has to reach the wider end. The floor area calculator adds up to six rectangles and subtracts what you mark, and the guide to measuring odd rooms covers L-shapes, bays and angled walls.
Step 2: choose the waste for your layout
Waste is the flooring that becomes offcuts, broken pieces and rejects. It depends first on the layout and then on the room.
| Layout | Tile, wood, laminate, vinyl | Add for |
|---|---|---|
| Straight or brick | 10% | closets and several doors +2%; a complex room +5% |
| Diagonal (45°) | 15% | a room under 50 sq ft +3% |
| Herringbone or chevron | 20% | a rustic wood grade or a printed pattern +5% |
Carpet and sheet vinyl are different: their waste is set by the roll width, not a percentage, and their calculators work it out from the strips. The waste factor calculator builds the percentage for your case, and the guide to waste factors explains each adjustment.
Step 3: multiply, then divide by the real coverage
Multiply the area by one plus the waste to get the area to order. Then divide by the coverage printed on the package. Not a typical coverage, not the one from the last floor you bought: the label on this product. Laminate boxes run from 17 to 25 square feet, vinyl plank from under 19 to over 30, and a 20% difference in coverage is a 20% difference in boxes. The coverage per box reference shows the usual ranges by material.
Step 4: round up once, and keep the spare
Round up to whole boxes once, at the end. The difference between the boxes bought and the area to order is spare, not waste, and it is worth keeping: a sealed box from the same production lot is the only way to repair the floor later with a matching piece. The boxes and cartons calculator shows the boxes before rounding, so you can see how much of the last box you will use, and adds a spare box and the cost if you want them.
Step 5: measure the walls for the trim
Baseboard, shoe moulding and carpet tack strip follow the walls, not the floor. Add the length of every wall, subtract the doorways, and add 10% for the corners. The perimeter calculator gives the run and the baseboard calculator the pieces.
A living room, start to finish
An L-shaped living room in vinyl plank
The room is a 16 × 12 ft main area with an 8 × 6 ft dining leg, a 6 × 3 ft closet, and a 4 × 2 ft raised hearth the floor stops at. The plank is 7 × 48 in with a pad attached, 23.6 sq ft per box, laid straight.
- Area: 192 + 48 + 18 − 8 = 250 sq ft
- Waste: 10% for a straight layout; area to order 250 × 1.10 = 275 sq ft
- Boxes: 275 ÷ 23.6 = 11.65, rounded up to 12 boxes (283 sq ft, about 120 planks)
- Spare: 283 − 250 = 33 sq ft, a little over a box
- Trim: the walls, closet included, add up to 74 ft; less one 3 ft door = 71 ft; with 10% that is 78 ft, or 10 lengths of 8 ft baseboard and the same of shoe moulding
Twelve boxes and ten lengths of each trim. Measured as one 16 × 18 ft rectangle the room would have ordered 13 boxes; measured without the closet, 11 and a trip back to the store.
The same method for other floors
Tile follows the same steps with one refinement: the tile count uses the tile plus its grout joint, which is slightly fewer tiles than the face area suggests, and boxes are counted by tiles per box. The floor tile calculator does both, and the guide to tile size and grout joint explains why.
Wood adds the grade to the waste: a select grade loses 5%, a rustic grade 15%. The hardwood calculator sets the waste from the grade and the layout together.
Carpet replaces steps 2 to 4 with strips: the room is covered by strips of a 12 ft roll, and the question is how many linear feet of roll, with how many seams. The carpet calculator lays the roll both ways and picks the better one.
Everything underneath follows the area: underlayment rolls, thinset bags, leveler bags and backer board sheets are all area divided by coverage, with their own small allowances. The guide to the units of flooring covers the conversions when a label or a quote uses square yards or square metres.
Three checks before you order
Is the area the room, without waste? If you added waste to the area and then the calculator adds it again, you will over-order by a box or two.
Is the coverage from the label? Typical figures are fine for a budget, not for an order.
Is it one lot? Check that every box carries the same lot or batch number before you open any, and keep the receipt for unopened returns.