Understanding your result
The headline is the boxes to buy, with the tiles and the fixing beside it. The table shows the tile size and area, the pattern with its waste, the tiles, the boxes, what they cover, and the tabs or tackifier.
Tiles is the floor area divided by one tile’s area, plus the pattern’s waste, rounded up. Carpet tiles are butted tightly with no joint, so there is nothing to add for spacing. Boxes follow the tiles per box on the label. Carpet tiles come in a few standard sizes: 24 × 24 in in the US, 50 × 50 cm internationally, and 25 × 100 cm planks, each with its own box count.
Fixing is the part that changes the shopping list. Tabs are small adhesive squares placed under the corners, about one per tile; they are tidy, quick and suit homes. Tackifier is a release adhesive rolled onto the floor and left to dry tacky; it covers about 200 sq ft per gallon. Loose lay relies on a heavy backing, and the note reminds you that edges and doorways still need fixing. For broadloom from a roll instead of tiles, the carpet calculator; for vinyl tiles, the LVT and peel-and-stick calculator; for the general box arithmetic, the boxes and cartons calculator.
How we calculate this
The pattern waste figures are installer and manufacturer rules of thumb: random is lowest because any tile fits anywhere, diagonal is highest because of the 45° cuts at every wall. They sit alongside the other materials on the waste factors reference. The guide to waste factors explains why tiles waste less than rolls, and the complete method for flooring quantities covers measuring.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Tile size | 24 × 24 in (50 × 50 cm metric) | Standard carpet tile formats (Interface, Shaw, Mohawk product pages, 2025) |
| Tiles per box | 16 | Common for 24 in and 50 cm tiles (16 to 20 per box) |
| Pattern waste | 3% random, 5% monolithic or quarter-turn, 10% diagonal | Installer and manufacturer rules of thumb |
| Tabs | about one per tile + 5% | Manufacturer guidance for corner tabs |
| Tackifier | 200 sq ft per gallon (4.9 m² per L) | Release adhesive data sheets: 150 to 250 with a roller |
Assumptions last reviewed October 8, 2026.
The calculator does not count transitions at doorways or the edge trim where tiles meet a hard floor. It assumes one tile and one colour; a pattern of several colours is counted per colour by running the calculator with each colour’s share of the area. It does not judge the subfloor, which for carpet tiles must be dry and reasonably flat, but need not be as perfect as for vinyl.
Two worked examples
A 30 × 20 ft basement family room, monolithic
24 in tiles, 16 per box at $58, tabs.
- Floor area: 600 sq ft; tiles 600 ÷ 4 × 1.05 = 157.5, rounded up to 158
- Boxes: 158 ÷ 16 = 9.9, rounded up to 10 boxes, $580
- Tabs: 158 × 1.05 = 166, one pack
Ten boxes give 160 tiles, two spare. Add an eleventh for repairs in a basement, where carpet tiles earn their keep: a wet corner is fixed by lifting and replacing four tiles.
420 sq ft of 50 cm tiles, random, loose-laid
20 tiles per box.
- Tile area: 2.69 sq ft; tiles 420 ÷ 2.69 × 1.03 = 160.8, rounded up to 161
- Boxes: 161 ÷ 20 = 8.05, rounded up to 9 boxes
- Fixing: none in the field; tabs at the doorways and edges
A random layout wastes least and hides any mismatch between boxes. The ninth box is mostly spare; the 19 extra tiles are a generous repair stock.
Where to find your inputs
Tile size and tiles per box. On the box; check whether the size is nominal (24 in) or metric (50 cm, 19.7 in).
Pattern. From the arrows on the back and the look you want: same way, alternating, or any way.
Fixing. The maker’s instructions name tabs, a specific tackifier, or loose lay.
Price. Per box; carpet tile is often quoted per square yard, so divide by the box coverage to compare.
Common mistakes
- Ignoring the arrows. A monolithic floor with a few tiles turned shows a patchwork. Check every tile.
- Loose-laying everything. Even heavy-backed tiles need fixing at doorways and edges.
- Permanent glue. It defeats the point of tiles. Use a release adhesive or tabs.
- No spare box. Replacing a tile later needs the same dye lot.
- Tiles on a damp slab. Moisture under carpet tile grows mould. Test basements first.
- Mixing tile sizes. A 24 in tile and a 50 cm tile are not the same size; check before mixing boxes.
Questions people ask
- How many carpet tiles for a 20 × 15 room?
- The room is 300 sq ft. In 24 inch tiles (4 sq ft) that is 75 tiles, 79 with 5% waste for a quarter-turn layout, and 5 boxes of 16. In 50 cm tiles (2.69 sq ft) it is 112 tiles, 118 with 5%.
- What waste for carpet tiles?
- About 3% for a random or non-directional layout, 5% for monolithic or quarter-turn, and 10% for diagonal installations or patterns made from several colours. Carpet tiles cut cleanly with a knife and offcuts are often reused, so the waste is low.
- What is quarter-turn carpet tile installation?
- Each tile is rotated 90 degrees from its neighbours, using the arrows on the back, so the pile direction alternates in a checkerboard. It hides the joints and makes a tile floor look deliberate rather than like broadloom. Monolithic keeps every arrow the same way and looks closest to broadloom.
- Do carpet tiles need glue?
- Most are installed with a release adhesive (tackifier) or with adhesive tabs at the corners, which hold the tiles in place but let them be lifted and replaced. Some heavy-backed tiles can be loose-laid in small rooms, though makers still want them fixed at doorways and edges.
- How many adhesive tabs do I need?
- About one per tile, placed where four tile corners meet, plus a few spare. A 300 sq ft room of 24 inch tiles needs about 83 tabs, which is part of one pack. Tabs come in packs of 250 to 1,000.
- Why buy an extra box of carpet tiles?
- Because the point of carpet tiles is replacing a stained or worn tile, and that only works with tiles from the same dye lot. A spare box stored flat is the cheapest repair kit on any floor.