Flooring Calculator
Enter the length and width of your room to find how much flooring to buy, including the 10% (straight) and 15% (diagonal) waste allowances recommended by the National Wood Flooring Association.
How to calculate flooring
Multiply the room's length by its width for the floor area in square feet, then add a waste allowance: about 10% for a standard straight-lay install and 15% for diagonal or patterned layouts. For odd-shaped rooms, split the floor into rectangles, total the areas, then add waste.
Flooring needed = Length ft × Width ft × (1 + waste %)
Worked example
A 12 ft × 12 ft room with standard straight-lay flooring.
- Area = 12 × 12 = 144 ft²
- Add 10% waste = 144 × 1.10
Result: 158.4 ft² to buy (144 ft² floor + 10% waste)
Frequently asked questions
How much flooring do I need?
Multiply the room's length by its width for the area in square feet, then add 10% for waste on a standard install (15% for diagonal patterns). A 12×12 room (144 ft²) needs about 158 ft² of flooring.
How much extra flooring should I buy?
The National Wood Flooring Association recommends 7–10% waste for straight installs, 12–15% for diagonal layouts, and up to 20% for herringbone or chevron patterns.
How many boxes of flooring do I need?
Divide the square footage (including waste) by the coverage printed on the box, usually 18–25 ft² per box, then round up. Always buy from the same lot number for consistent color.
How do I measure an irregular room?
Split the floor into rectangles, calculate each one's area (length × width), add them together, then apply your waste percentage to the total.
Why do I need a waste allowance?
Cutting planks to fit at walls, around doorways, and at the ends of rows produces off-cuts you can't always reuse. The waste allowance covers these plus a few spare planks for future repairs.