Flooring square footage calculator
Short answer
To calculate flooring square footage, measure each room’s length and width in feet and multiply them, then add all the rooms together. A 12 × 15 room is 180 sq ft. Add about 10% for waste (15–20% for a diagonal or herringbone layout) and round up to full boxes. Three rooms totaling 400 sq ft means buying about 440 sq ft.
Measure each room’s length and width in feet, add a room for L-shapes, and we total the square footage plus a waste allowance for cuts.
Square footage by room size
| Room (ft) | Square feet | Buy (+10% waste) |
|---|---|---|
| 10 × 10 | 100 sq ft | 111 sq ft |
| 10 × 12 | 120 sq ft | 132 sq ft |
| 12 × 12 | 144 sq ft | 159 sq ft |
| 12 × 15 | 180 sq ft | 199 sq ft |
| 15 × 15 | 225 sq ft | 248 sq ft |
| 12 × 20 | 240 sq ft | 264 sq ft |
| 15 × 20 | 300 sq ft | 330 sq ft |
| 20 × 20 | 400 sq ft | 441 sq ft |
How to calculate flooring square footage
Flooring is sold by the square foot, so the first step in any flooring project is measuring your space. For each room, measure the length and width in feet and multiply them — that’s the room’s square footage. A 12-foot by 15-foot room is 180 square feet. For a whole floor, measure every room you’re covering and add the totals.
For L-shaped or irregular rooms, split the space into rectangles, measure each, and add them. Then add a waste allowance — about 10% for a straight lay, 15% for a diagonal layout, and 20% for herringbone — and round up to whole boxes. The waste covers cuts, the odd damaged plank, and a few spares for future repairs.
Now get boxes & cost
Have your square footage? The main calculator turns it into boxes to buy and an installed cost by material and pattern.
Open the flooring calculatorFrequently asked questions
How do I calculate flooring square footage?
Measure each room’s length and width in feet and multiply them to get that room’s square footage, then add the rooms together. A 12 × 15 room is 180 sq ft. Add about 10% for waste and round up to whole boxes. The calculator above totals multiple rooms for you.
How much extra flooring should I buy for waste?
Add about 10% over your measured square footage for a standard straight lay, 15% for a diagonal (45°) layout, and 20% for herringbone or chevron. The extra covers cuts, defects, and future repairs. Always round up to full boxes.
How do I measure an L-shaped or irregular room?
Split the space into rectangles, measure each one’s length and width, and add the areas together. In the calculator, use “Add a room” for each rectangle — the total is the sum.
How many square feet is a 12x12 room?
A 12 × 12 room is 144 square feet (12 × 12). With a 10% waste allowance you’d buy about 159 sq ft of flooring.
Do I include closets and doorways in the square footage?
Include any closet or alcove you’re actually flooring — measure it as its own small rectangle. You can ignore tiny doorway notches; rounding up to full boxes and the waste allowance cover minor extras.