Flooring Calculator
Enter the room size, a waste allowance and how much a box covers. We tell you how many boxes to buy.
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The formula
Boxes = (length x width x (1 + waste %)) / coverage per box, rounded up.
Why you need extra
Cuts at the walls, damaged planks and pattern matching all create waste. A common allowance is 10 percent for straight layouts and 15 percent for diagonal or patterned ones. Buying a little extra also means you have spares for repairs later.
An example
A 12 by 15 ft room is 180 sq ft. With 10 percent waste you need 198 sq ft. If each box covers 20 sq ft, that is 9.9 boxes, so you buy 10.
Before you order
- Measure the longest and widest points of the room, and add alcoves.
- Buy all boxes at once so the batch and shade match.
- Let boxes acclimatise in the room, as the manufacturer advises.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| Room length (ft): 12; Room width (ft): 15; Waste allowance (%): 10; Coverage per box (sq ft): 20 | Boxes to buy: 10 |
| Room length (ft): 18; Room width (ft): 22; Waste allowance (%): 15; Coverage per box (sq ft): 24 | Boxes to buy: 19 |
| Room length (ft): 8; Room width (ft): 10; Waste allowance (%): 10; Coverage per box (sq ft): 19.5 | Boxes to buy: 5 |
Flooring Calculator: frequently asked questions
What waste percentage should I use?
10 percent for simple rooms, 15 percent for diagonal layouts, herringbone or lots of corners.
How accurate is this estimate?
It is as accurate as the numbers you give it. Real-world amounts such as paint, concrete or fuel vary, so allow a margin.
Is what I enter in this tool saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this tool free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026