How to use the flooring calculator
- Measure each room wall to wall at floor level, as feet and inches. 10 ft 6 in goes in as 10 and 6. Add another row for each room, hallway or closet that gets the same floor.
- Set the waste allowance. 10% is filled in. Change it to the figure your installer or the flooring maker gives for your product and layout.
- Type what one box covers. Flooring boxes state their coverage, for example "22 sq ft per box". The calculator divides and rounds up to whole boxes.
- For tiles, open Tile count and enter the tile size and the grout gap to see how many tiles that is.
- For cost, open Cost and enter the price per box or per square foot.
Choose Meters to enter meters and centimeters, box coverage in square meters, tile sizes in centimeters and the grout gap in millimeters.
How the number of boxes is worked out
- Floor area = length x width for each room, added together. Inches are divided by 12 first, so 10 ft 6 in is 10.5 ft.
- Area to buy = floor area x (1 + waste percent / 100).
- Boxes = area to buy / coverage of one box, rounded up to a whole box.
Example: a room 12 ft by 10 ft 6 in, 10% waste, and a box that covers 22 sq ft. Press Try an example to fill it in.
| Step | Working | Result |
|---|---|---|
| Floor area | 12 x 10.5 | 126 sq ft |
| With 10% waste | 126 x 1.10 | 138.6 sq ft |
| Boxes | 138.6 / 22 = 6.3, rounded up | 7 boxes |
| Boxes cover | 7 x 22 | 154 sq ft |
| Left over | 154 - 138.6 | 15.4 sq ft |
| Cost at $45 a box | 7 x 45 | $315.00 |
If the price is per square foot, you still pay for whole boxes, so the calculator prices the area of the boxes you buy: at $2.10 per sq ft, 154 x 2.10 = $323.40. If you have not entered a box size yet, it prices the area with waste instead.
How much waste to allow
Boards and tiles are cut at walls, doorways and corners, and the offcuts cannot always be used elsewhere. Adding 5 to 10 percent is a common allowance, not a rule. What you need depends on the product, the room and the layout:
- A plain rectangular room laid straight usually needs the least.
- Diagonal layouts need more, because every row ends in an angled cut against the wall.
- Herringbone and other patterns, large tiles, and rooms with many corners or doorways also need more.
The best figure is the one your installer or the flooring maker gives for that product and that layout. A few spare pieces left over are also useful if a board or tile has to be replaced later.
Counting tiles with a grout gap
Each tile takes up its own size plus one grout gap in each direction. So the space one tile fills is (tile length + gap) x (tile width + gap). The number of tiles is the area to buy divided by that space, rounded up.
| Tile | Grout gap | Space per tile | Tiles for 138.6 sq ft |
|---|---|---|---|
| 12 x 24 in | 1/8 in | 12.125 x 24.125 = 292.52 sq in = 2.031 sq ft | 69 |
| 12 x 12 in | none | 144 sq in = 1 sq ft | 139 |
There are 144 square inches in a square foot, because a foot is 12 inches. The grout gap makes each tile cover slightly more floor, so fewer tiles are needed than with no gap. Type the gap as a fraction, such as 1/8 or 3/16, or as a decimal.
The count includes your waste allowance but cannot know how the cut pieces fall in your room. If your tiles come in boxes, enter the coverage of one box as well to see how many boxes that is.
Measuring in meters (UK and elsewhere)
Choose Meters. A room 4 m by 3.5 m is 14 m². With 10% waste that is 15.4 m². If a pack covers 2.2 m², 15.4 / 2.2 is exactly 7 packs, and the calculator does not add an extra one for tiny rounding errors in the arithmetic.
For 60 x 60 cm tiles with a 3 mm gap, each tile takes 60.3 x 60.3 cm, or 0.3636 m², so 15.4 m² needs 43 tiles. The result also shows the area in square feet, using the exact definition of the foot: NIST states "1 foot = 0.304 8 meter exactly", so one square foot is 0.09290304 m².
Questions and answers
How many boxes of flooring do I need?
Multiply length by width for each room and add them up, add your waste allowance, then divide by the area one box covers and round up. A 12 ft by 10 ft 6 in room is 126 sq ft; with 10% waste it is 138.6 sq ft, which is 7 boxes of 22 sq ft.
How much extra flooring or tile should I buy?
Many people add 5 to 10 percent. That is a common allowance, not a rule. Diagonal and patterned layouts, and rooms with many corners, need more. Use the figure your installer or the flooring maker gives.
How many tiles do I need for 100 square feet?
With 12 x 12 inch tiles and no grout gap, one tile is one square foot, so 100 tiles plus your waste allowance: 110 tiles with 10%. With a grout gap, each tile covers a little more floor, so slightly fewer tiles are needed.
Does the grout gap change how many tiles I need?
Yes, slightly. Each tile fills its own size plus one gap each way. A 12 x 24 inch tile with a 1/8 inch gap fills 12.125 x 24.125 inches, which is 2.031 square feet instead of 2.
How do I convert square feet to square meters?
Multiply by 0.09290304, because a foot is exactly 0.3048 m. 100 square feet is 9.29 m². To go the other way, divide by 0.09290304, so 1 m² is about 10.764 square feet.
Sources
Checked on 7 October 2026. If a rule has changed, please tell us.