Tile and grout estimator

How the calculation works

Tile count is the area with wastage divided by the footprint of one tile including its share of the grout joint, rounded up to a whole tile. Wastage comes from the lay pattern — about 10% straight, 12% brick bond, 15% diagonal, 20% herringbone — plus 2% for tiles 600 mm or larger and 5% for rooms under 3 m². Enter a box size and the boxes are counted in tiles, not in square metres, which is what keeps a narrow room from being short-ordered.

Adhesive coverage follows the trowel notch rather than the tile: a 20 kg bag covers about 11 m² at 6 mm, 7 m² at 10 mm and 4.5 m² at 12 mm. We suggest a notch from your tile size, add 10% application waste, and add 20% more when the tiles are back-buttered. Grout kilograms come from the joint volume per square metre — ((tile length + tile width) ÷ (tile length × tile width)) × joint width × tile thickness — multiplied by a mixed density of 2100 kg/m³, plus 15% for what the bucket, float and sponge take. Both round up to whole bags.

Updated methodology. This estimator previously used a flat 4 kg/m² adhesive figure and a grout density of 1.6 g/cm³, and ignored the lay pattern. Both have changed: adhesive is now read off the trowel notch, and the grout density is 2100 kg/m³, back-solved from Australian manufacturer coverage tables — the old constant under-ordered grout by roughly 30% against those tables. Tile counts also account for the grout joint. If you have quoted off this page before, expect the grout and adhesive figures to be higher.

For multi-room jobs (bathrooms, ensuites and living areas in the same project), mark each room from the floor plan in AreaSum and the report rolls totals up per material so adhesive and grout figures stay accurate. See how it works.

See also: tile wastage by pattern, grout coverage, trowel notch, lippage, dye lot, box coverage — or the audience guide for tile installers.

Tiles, adhesive & grout — frequently asked questions

How much grout do I need per square metre?

It depends on tile size, joint width and tile thickness — smaller tiles and wider joints use far more grout, because grout fills joint volume rather than covering area. As a guide, 300 × 300 × 8 mm floor tiles with a 3 mm joint use about 0.34 kg/m² before waste. The estimator computes the exact figure from your inputs and rounds it to whole bags.

How much tile adhesive do I need?

Adhesive coverage is set by the trowel notch, not by the tile. A 20 kg bag covers roughly 11 m² at a 6 mm notch, about 7 m² at 10 mm and under 5 m² at 12 mm. The estimator suggests a notch from your tile size, adds 10% application waste, and adds a further 20% if the tiles are back-buttered.

How do I calculate how many floor tiles I need?

Divide the area by the footprint of one tile including its share of the grout joint, add the wastage for your lay pattern, then round up to whole tiles. A 20 m² floor of 600 × 600 mm tiles at 12% wastage is 62 tiles. If you enter the box size, the estimator then counts boxes in tiles rather than in square metres, which is what stops a narrow room being short-ordered.

How much wastage should I allow for floor tiles?

It depends mostly on the lay pattern: about 10% for a straight grid, 12% for a 50% brick bond, 15% for a diagonal lay and at least 20% for herringbone — Australian retailers publish 20 to 30% for herringbone. Add roughly 2% for tiles 600 mm or larger, and about 5% for rooms under 3 m², where the floor is nearly all perimeter cuts.

How is the grout quantity calculated?

From the joint volume per square metre: ((tile length + tile width) ÷ (tile length × tile width)) × joint width × tile thickness, multiplied by the density of mixed cementitious grout — about 2100 kg/m³, back-solved from Australian manufacturer coverage tables. A further 15% is added for what is lost to the bucket, float and sponge.

Why should I order all the tiles in one batch?

Tiles are fired in production runs, and shade and calibre (the actual fired size) both drift between runs. A top-up order placed later usually arrives from a different batch and will not match on a continuous floor. Work out the full quantity including wastage, order it in one go from a single batch, and keep the spares for repairs.

Does this work for wall tiling?

Yes — switch the surface to wall. That drops the default grout joint from 3 mm to 1.5 mm, sets the trowel to a 6 mm notch regardless of tile size, and turns off the back-butter suggestion and the movement-joint advisory, which are floor concerns.