Floor tile quantity:
area, wastage and rounding up to full boxes

Start from coverage, not from a guess

The number of tiles is the floor area divided by the area one tile covers, plus a margin for the pieces you will cut and the ones that crack. Measure the floor in the same units as the tile, convert if needed, and keep the sums in square metres until the end.

For rooms that are not simple rectangles, split the plan into rectangles, calculate each and add them. Subtract fixed items such as a built-in wardrobe base only if the tile will not run under it.

Plan the layout before trusting the arithmetic. If the room is 4.0 m wide and a tile is 0.6 m, there are six whole tiles and a 0.4 m remainder. Splitting the remainder across both walls gives two 0.2 m cut tiles, which are thin and fragile. Centring the pattern on a doorway or shifting the start line can avoid slivers and sometimes reduces the cut count.

The tile quantity formula

Round only at the end. Rounding the base count up first and then applying the allowance can add a tile or two you did not need.

If you prefer working in feet, convert first: 1 m² is 10.764 ft², and a 2 ft × 2 ft tile covers 4 ft². A 258 ft² floor then needs 258 ÷ 4 = 64.5 tiles before allowance. Mixing metres for the room and inches for the tile is the most frequent source of a wildly wrong count.

Worked example: a 24 m² floor

If the same room used 0.6 m × 1.2 m tiles, each covering 0.72 m², the plain count is 33.33 and with 10% allowance 36.67, so 37 tiles.

With a 3 mm grout joint the effective pitch of a 600 mm tile is 603 mm, so the real count for a 6 m run is 9.95 tiles across, which rounds to 10 and is the same as the plain division. On very large floors the joints can add up to an extra row, so allow a little more there.

Choosing the wastage allowance

These are common rules of thumb rather than standards, so ask your installer for their figure. A professional will often cut tiles so that the offcut is reused on the other side of the room, which lowers real wastage below the allowance.

Measuring an awkward room

Few rooms are clean rectangles. An L-shaped hall is two rectangles added together, a bay window is a small rectangle sticking out, and a doorway is a thin strip of floor that is easy to forget. Sketch the outline, label each side in metres and break it into simple pieces.

Measure twice. A 2 cm error on each side of a 6 m by 4 m room changes the area by more than half a square metre, enough to shift the tile count by one or two.

Rounding up to full boxes

Tiles are sold in cartons with a fixed count or area. If a box holds 4 tiles of this size, 74 tiles is 18.5 boxes, so you buy 19 boxes and receive 76 tiles. The two extra become part of your spare stock.

Buy everything from the same batch. Shade and size can differ slightly between production runs, and a top-up order months later may not match. Keeping a few unused tiles from the batch is also practical for later repairs, since the style may be discontinued.

Check the box label for the shade, calibre and batch code before accepting delivery. Calibre is the actual size grade of the tile, and tiles from two different calibres in one floor produce uneven joints. Opening the boxes on site and laying a few tiles side by side before fixing begins is a cheap way to catch a shade mismatch.

Check these before placing the order

• Joint width: the grout line adds to the pitch of the tiles, so a 3 mm joint on 600 mm tiles shifts the count very slightly on large floors.
• Skirting: if you will tile the skirting from the same box, add its running length separately.
• Level and slope: wet-area falls waste material at the drain, so add to the allowance.
• Direction and pattern: a plan of the layout helps the installer choose a start line that avoids thin cuts at the walls.

How tile size changes the order

Larger tiles cover more per piece but waste more on cuts in small rooms. A 600 × 1,200 mm tile has an area of 0.72 m², so the 24 m² floor needs 37 pieces against 74 of the smaller size. In a narrow bathroom, though, the long tiles may need a cut on nearly every piece, which pushes the real wastage up and makes the smaller tile the cheaper choice.

Price is usually quoted per square metre or per box, so compare on the area you will pay for. A box that covers 1.44 m² at ₹1,000 costs about ₹694 per m², and the box count you need follows from dividing your total area including allowance by 1.44 and rounding up.