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How to Measure Flooring Square Footage: Rooms, Closets, L-Shapes, Waste by Layout, Boxes, Dye Lots and the Box You Keep in the Basement
Flooring & Tile
Measuring for Flooring: The Rooms, the Waste, the Boxes, and Why the Order Is Always Bigger Than the Room
Length times width gets you the floor. It does not get you the order, because planks come in boxes, boxes come in fixed sizes, every row ends in a cut, and the offcut from one wall rarely fits the next. An installer orders 10% over for a straight lay, 15% for a herringbone, and then adds a box he does not tell you about. Here is how to measure a house his way: every room, every closet, the L-shapes, the stairs, and the waste by layout, so the yard delivers once and the floor matches itself.
Measuring a room
- Measure wall to wall at the widest point, in inches, under the baseboard if it is coming off, to the face of it if it is not. Round each dimension up to the next whole inch. Length times width, divided by 144, is the square footage.
- Add the closets. They get the same floor and people forget them every time. A 2 by 6 closet is 12 sq ft, a walk-in is 40.
- Add the doorways. The floor runs into every door opening to the centre of the door, about 1 sq ft each. Six doors is a 6 sq ft line item you did not have.
- Break an L or a T into rectangles and add them. Never measure the longest two walls and multiply; you will be 20% over on an L and the yard does not take back opened boxes.
- Deduct nothing for islands, fireplaces or vanities you are keeping. The flooring goes under the toe-kick and up to the hearth, and the cut-around makes more waste than the deduction saves.
- Draw it. A sketch with the dimensions on it is what the installer wants anyway, and it is how you catch the hall you forgot.
Waste, by how the floor is laid
| Layout | Add | Why |
|---|---|---|
| Plank, straight lay, square room | 10% | End cuts, a damaged plank or two per box, the last row ripped to width. |
| Plank, straight lay, many rooms and angles | 12% | Every doorway and jog is a cut that does not carry over. |
| Plank, diagonal or herringbone | 15% | Every row starts and ends in a triangle. The triangles do not fit anywhere. |
| Tile, straight lay | 12% | Perimeter cuts plus breakage. 12×24 wastes more than 12×12 in a small room. |
| Tile, diagonal, herringbone or pattern | 18% | Half the perimeter tiles are two cuts each. Large format on a diagonal can hit 20%. |
| Carpet | Measured on the roll | See below. The room area is the wrong number. |
These are the waste figures the flooring cost calculator applies to the material line, not to the labour. Labour is on the finished floor; the installer does not charge to install the scrap.
From square feet to boxes
Boxes vary by product, so read the label, but the usual sizes are: engineered hardwood 18 to 24 sq ft a box, 5-in. planks commonly about 20; vinyl plank 20 to 28, often 23.6; laminate 18 to 22; 12×24 porcelain in boxes of 8 tiles, 16 sq ft. Divide the area with waste by the box size and round up to the next whole box. Then think about adding one more.
| Space | Area | With waste | Boxes |
|---|---|---|---|
| 12×14 bedroom plus a 2×6 closet, engineered plank, straight | 168 + 12 = 180 sq ft | 180 x 1.10 = 198 | 10 boxes at 20 sq ft = 200 sq ft |
| The same bedroom, herringbone | 180 sq ft | 180 x 1.15 = 207 | 11 boxes at 20 sq ft = 220 sq ft |
| The same bedroom, 12×24 porcelain, straight | 180 sq ft | 180 x 1.12 = 201.6 | 13 boxes at 16 sq ft = 208 sq ft |
| L-shaped living and dining, 16×20 plus 10×12, vinyl plank | 320 + 120 = 440 sq ft | 440 x 1.12 = 492.8 | 21 boxes at 23.6 sq ft = 495.6 sq ft |
The bedroom in porcelain at mid grade is 208 sq ft of tile at $4.50, so $936 of material for a 180 sq ft floor; the setter’s $10.00 is on the 180. That is how a quote gets two different square footages on it and both are right.
Carpet, stairs and the things measured differently
Carpet comes on a 12-ft roll (some 13 ft 6 in., some 15 ft) and is cut across the roll, so a room is measured as the piece of roll that covers it. An 11 by 10 bedroom needs a 12 by 10 cut, 120 sq ft, not 110, and the 1-ft strip is scrap. A 12 by 11 needs exactly 12 by 11. A 14 by 16 room needs a 12 by 16 piece plus a 12 by 16 piece cut into 2-ft strips and seamed, or a 15-ft roll, and the installer decides which. This is why carpet is priced installed and nobody quotes the material alone. Carpet costs.
Stairs are counted, not measured: the number of treads, whether the ends are boxed or open, and the width over 42 in. Landings are measured as floor. A box of hardwood for the landing comes from the same dye lot as the main floor or the landing will be a different colour in the afternoon. Stairs.
Showers and tub surrounds are square feet of wall, each wall measured, with 12% to 18% waste depending on the pattern, and the floor of the shower separately at a mosaic rate. The tile and shower calculator does the walls.
Dye lots and the box you keep
Every run of flooring has a lot or batch number on the box. Two lots of the same product are the same product in the catalogue and a shade apart on the floor, and the line between them will run across your living room. Order the whole job at once from one lot, check the labels when it is delivered, and refuse a mixed delivery before it is opened. If the yard is short a box and offers to send one from the next lot, the installer blends it into a closet.
Then keep a box. Not the scraps, a sealed box, in the basement, labelled with the room and the date. In eight years when the dishwasher leaks or the dog does something, the product will be discontinued and your spare box is the only repair that matches. On a $5.25 plank that box is about $105 of insurance against a repair that otherwise means redoing the room.
Questions people ask
How much extra flooring should I order?
10% for a straight-laid plank in a simple room, 12% for tile or a cut-up floor plan, 15% for diagonal or herringbone plank, 18% for a tile pattern, then round up to whole boxes and keep one sealed box for repairs.
How many boxes of flooring do I need for a 12×12 room?
144 sq ft plus 10% is 158.4; at 20 sq ft a box that is 8 boxes (160 sq ft). At 23.6 sq ft a box, 7 boxes (165.2 sq ft). Read the box size on the label; they vary by product and plank width.
Do I measure under the baseboard?
If the baseboard is coming off, measure wall to wall. If it is staying and quarter-round will cover the gap, measure to the face of the baseboard. The difference is about 1 in. each side and it only matters on the last row.
Should I let the installer measure?
Yes, and measure yourself first. His number will be a little higher than yours and that is the waste. If it is a lot higher, ask him to walk you through the sketch. A measure that is 25% over the room area is either a herringbone or a mistake.
Does the installer charge for the waste?
He charges labour on the finished floor area and material on the ordered quantity, so you pay for the waste as material only. A quote that charges labour on the boxes delivered is overcharging by the waste percentage.
Let the calculator do the arithmetic
The flooring cost calculator takes your room dimensions, applies the right waste to the material, prices the labour on the floor and gives you the installed number with HST. For a new build or a big renovation with drawings, the $249 plan takeoff measures every room from the plans so you are not up a stepladder with a tape.
Sources and further reading
- National Wood Flooring Association: the installation guidelines every hardwood warranty points to: subfloor flatness, moisture limits, acclimation, fastening schedules and the radiant-heat chapter.
- Tile Council of North America: the TCNA Handbook methods for tile over wood, concrete and in showers, and the ANSI lippage and grout standards a tile setter is held to.
- Mirage Hardwood Floors: Quebec-made solid and engineered hardwood; their installation guides give the moisture, acclimation and radiant limits in plain numbers.
