About this calculator
This calculator helps estimate how many ceiling tiles a room needs — choose the room shape (rectangle, one of four non-rectangular templates, or a freely sketched shape), enter the tile size and the joint width. Works for polyurethane, polystyrene, or other glued-on ceiling tiles.
Formula
The room shape is entered through the shared roomShape field: five fixed templates
(rectangle, L-shape, alcove/niche, T-shape, U-shape) or a freely sketched shape (up to 10
added/subtracted rectangles) — the same mechanism as the floor-tile calculator. The room
area is always computed from the true polygon outline, not a single length×width
figure — for the rectangle template this gives the same result as this calculator's older
version with separate length/width fields, but for any non-rectangular template the area is
exact, not a bounding-box estimate. The tile, adhesive, and grout formulas don't depend on
this — they always used the room area as a single number:
tile "pitch" = (tile length + joint width) × (tile width + joint width)
tiles required (excl. waste) = ceil(room area / pitch)
waste tiles = ceil(tile count × waste% / 100)
total tiles = tile count + waste tiles
Adhesive quantity: room area × adhesive coverage (kg/m²). Grout (joint) quantity is
computed from exact geometry — within one pitch "cell", the joint area is pitch - tile area; that fraction, multiplied by the joint depth and density, gives the mass. Neither the
adhesive coverage nor the grout density comes from a standard or a manufacturer figure —
both are user inputs with sensible defaults.
Worked example
Defaults: room shape — rectangle 4 × 3 m (the template's own default dimensions), tile 300×300 mm, joint 3 mm, waste 10%, adhesive coverage 4 kg/m², joint depth 8 mm, grout density 1.6 kg/l.
room area = 4 m × 3 m = 12 m²
pitch = (300+3) mm × (300+3) mm = 303 × 303 = 91,809 mm²
tiles per m² = round(1,000,000 / 91,809) = 11
tiles excl. waste = ceil(12,000,000 / 91,809) = 131
waste tiles = ceil(131 × 10 / 100) = 14
total tiles = 131 + 14 = 145
adhesive = 12,000,000 mm² × 4 kg/m² = 48,000,000 mg = 48 kg
joint area per cell = 91,809 - (300×300) = 1,809 mm²
grout ≈ 3,026,526 mg ≈ 3.03 kg
For these inputs the calculator returns exactly this: 145 tiles total (131 excl. waste + 14 for waste), 11 tiles/m², 48 kg of adhesive, and about 3.03 kg of grout.
FAQ
Are light-fixture cutouts or other openings deducted from the area? No. The calculator has no opening list — the whole room area is treated as tileable. Light fixture positions need to be accounted for separately.
How much waste should be allowed for ceiling tiling? The default is 10%, adjustable from 0 to 50. The real requirement depends on the ceiling shape (niches, cornices) and edge trimming.
Why does the calculator warn about the joint width? When the joint is thinner than 1.5 mm or thicker than 12 mm, a warning is shown — this is only a practical guideline, not a limit: the calculator still uses exactly the value you entered.
What determines the adhesive and grout coverage? Adhesive coverage (kg/m²) and grout density (kg/l) are values you enter, with sensible defaults — they depend on the specific product, so the calculator doesn't derive them from any standard.
Can I use rectangular tiles instead of square ones? Yes — tile length and width are entered separately, so the calculator works equally well for square and rectangular tiles.
Why aren't there separate room length and width fields?
Because they were replaced by the shared room-shape (roomShape) field — the rectangle
remains one of five templates (its own two dimensions match the old length/width fields'
own values and bounds exactly), and the four other templates plus the free-form shape let
the calculator compute tile quantities for a non-rectangular room too, with no loss of
accuracy.
Assumptions and limits
No standard was found for a ceiling-tile quantity/area calculation — it's a plain geometric
problem, not an engineering calculation, so meta.standards is deliberately left empty.
Adhesive coverage, joint depth, and grout density are user inputs with sensible defaults, not constants derived from a standard.
The room area is always computed from the true polygon outline of the chosen shape (five templates, or a free-form add/subtract-rectangle shape), not from a single bounding rectangle — the same logic as the floor-tile calculator, since here too the math depends only on the total area, with no perimeter dependency. The calculator has no opening (light fixture, ventilation grille) list — the whole room area is treated as tileable. Laying is modeled as a straight grid with no offset pattern. The drawing shows tiles to scale, including cut tiles at the edges, but the total quantity is always calculated from area, not a count of the tiles drawn. The drawing is also schematic: for a large room, the row/column count is decimated so the SVG stays legible — neither affects the tile quantity calculation itself.