How much flooring do I need?
Short answer
Multiply the room's square footage by one plus a waste fraction (0.05 to 0.10 for a straight lay, 0.15 or more for diagonal or patterned layouts), divide by the coverage printed on each box, and round up to the next whole box. A 300 sq ft room with 10 percent waste and 20 sq ft boxes needs 17 boxes.
Start with the room square footage
Measure length and width in feet and multiply. A 15 ft by 20 ft room is 300 square feet. For anything that is not a plain rectangle, split the floor into rectangles, calculate each, and add them up. Include closets, alcoves, and doorway thresholds only if you actually plan to floor them.
This measured area is what you have to cover, not what you buy. Every install loses material to cuts and trimming, so the order quantity always lands above the measured number.
- Measure at floor level, not against a counter or wall cabinet that stops short of the wall.
- Round each measurement up to the nearest few inches, never down.
- For an L-shaped room, break it into two rectangles and total them.
Add a waste percentage
Waste covers edge cuts, trimming along walls, the occasional broken plank, and normal installer error. The amount depends mainly on the layout and the room's shape, not its size.
A straight lay running parallel to the walls wastes the least, so 5 to 10 percent usually covers it. Diagonal, herringbone, chevron, and other repeating patterns force angled cuts and short offcuts you cannot reuse, so plan on 15 percent or more. Lots of corners, jogs, or angled walls also push the figure up, since every edge is another cut.
- Straight lay in a simple rectangular room: 5 to 10 percent.
- Diagonal or patterned layout: 15 percent or more.
- Many corners, closets, and angled walls: lean toward the higher end.
Convert the total to boxes or cases
Flooring sells by the box or case, each covering a fixed area printed on the label. Divide your waste-adjusted square footage by the coverage per box, then round up to the next whole box. You cannot buy a partial box, and rounding down leaves you short mid-install.
Round up even when the division lands clean. The final cut row almost never falls on a full plank, so that extra box becomes your cutting margin.
The formula
Two steps: find how much flooring you need, then convert it to boxes.
Flooring needed = room square footage x (1 + waste fraction). Boxes needed = flooring needed / coverage per box, always rounded up to the next whole box.
Where room square footage is length x width of the floor you plan to cover, the waste fraction is extra material as a decimal (0.10 for 10 percent), and coverage per box is the area one box covers as printed on the label.
Worked example
A 15 ft by 20 ft room is 300 square feet to cover.
Add 10 percent waste for a straight lay: 300 x 1.10 = 330 square feet.
If each box covers 20 square feet: 330 / 20 = 16.5. Round up to 17 boxes. The half box past 16.5 becomes your cutting margin and leftover stock.
Why the extra material matters
The waste percentage is what keeps a job from stalling, not padding for the store.
Cut rows at the room's edges turn full planks into partial ones, and the leftover ends often fit nowhere else. Boards arrive with defects, and a saw cut occasionally goes wrong. Keeping a spare box or two also matters later: if a plank is ever gouged or water-damaged, a leftover from the same run is the most reliable way to match it, because color and grain can shift between batches even under one product name.
Treat these figures as estimates only. They get you a confident order quantity, but your exact needs depend on the room's shape, the installer's technique, and the specific product, so read the coverage on the actual boxes before buying.
Common mistakes
A handful of errors show up again and again, each one costing a second trip to the store or a mismatched patch down the line.
- Ordering the exact square footage. Buying 300 sq ft for a 300 sq ft room leaves nothing for cuts, and you run out before the last row.
- Using a straight-lay buffer for a pattern. A 10 percent buffer on a diagonal or herringbone floor almost guarantees a shortfall; use 15 percent or more.
- Mixing batches. Buy all your boxes at once from the same batch; topping up later risks a visible color mismatch.
- Forgetting to round up to whole boxes. Any leftover fraction means one more full box.
- Measuring only the open floor and skipping closets, alcoves, or thresholds you intend to cover.
Frequently Asked Questions
How much waste should I add for a diagonal or herringbone floor?+
Plan on 15 percent or more, versus 5 to 10 percent for a straight lay. Angled and patterned installs produce more short offcuts that cannot be reused, so material disappears faster than the raw area suggests. For an intricate herringbone in a room with many corners, some installers go well past 15 percent.
Why buy all the flooring from the same batch?+
Flooring is produced in batches, and color and grain can shift slightly between production runs of the same product. Buying every box together from one batch keeps the floor uniform. Boxes bought months later may not match, which is why holding back a spare box from the original order is worth it for future repairs.
What if the box coverage does not divide evenly into my square footage?+
That is expected. Divide your waste-adjusted square footage by the coverage per box and round up every time. In the worked example, 330 divided by 20 is 16.5, so you buy 17 boxes. The leftover fraction becomes your cutting margin and spare stock.
Does the waste percentage go on the raw room size or the finished total?+
On the raw room square footage. Multiply the measured area by one plus the waste fraction first, then divide by box coverage. In the example the 10 percent is added to 300 sq ft to get 330 sq ft, and only then do you convert to boxes.
Should I include closets and doorways in my measurement?+
Include only the space you actually plan to floor, such as closets, alcoves, and thresholds, since each adds square footage and extra cuts. Break oddly shaped areas into rectangles, calculate each, and total them before applying the waste percentage.
Skip the math
Enter your numbers and the Flooring Calculator does the work for you — free, and it runs entirely in your browser.
Open the free Flooring Calculator