Mosaic Tile Calculator

How many mosaic sheets do I need?

A sheet is laid with a grout joint all around it, so it covers its own size plus one joint each way. A 300 × 300 mm sheet with 2 mm joints covers 0.302 × 0.302 = 0.091 m², about 11 sheets per m². Divide the floor area plus waste by that coverage and round up; with the sheets per box entered, you get whole boxes. If the box states its coverage, enter that instead.

Waste is lower than for large tiles because sheets are cut along the joints: 10% by default. Loose hexagon tiles, where every cut at the wall is angled, default to 15%.

Hexagon tiles: measuring flat to flat

Hexagons are sized across the flats, from one side to the opposite side. If yours is labelled by the distance between opposite points, tick “measured point to point” and the size is multiplied by √3/2 (0.866). A 50 mm hexagon measured flat to flat is about 58 mm point to point.

The mosaic formulas

sheets = ⌈A × (1 + waste) ÷ ((a + j)(b + j))⌉; G_hex = 2 × j × d × ρ ÷ s; G_penny = f × d × ρ

a × b is the sheet size, j the joint, s the hexagon size flat to flat, d the joint depth (the tile thickness), ρ the grout density and f the share of the surface between the pennies: f = 1 − (π × D² ÷ 4) ÷ c, with c = √3/2 × (D + j)² for staggered pennies or (D + j)² on a square grid.

Worked example

Area 3 m² of 19 mm penny rounds, 3 mm spacing, 6 mm deep, staggered, on 300 × 300 mm sheets with 2 mm joints.
Each sheet covers 302 × 302 mm = 0.0912 m²; 3 × 1.10 ÷ 0.0912 = 36.2 → 37 sheets.
f = 1 − 283.5 ÷ 419.2 = 0.324; G = 0.324 × 6 × 1.6 = 3.1 kg/m².
Grout: 3 × 3.1 × 1.15 = 10.7 kg.

How much grout for penny round and hexagon mosaic

Small pieces mean much more joint per square metre. For square and rectangular tiles the grout rate is (L + W) ÷ (L × W) × joint width × depth × density, as in the grout calculator. Hexagons have twice the joint length of a square of the same size. Penny rounds are different again: the gaps between circles are wide, so grout fills a fixed share of the surface — about a third with staggered pennies.

19 mm pennies with 3 mm spacing take about 3.1 kg of grout per m² at 6 mm deep. 25 mm hexagons with 2 mm joints take about 1.5 kg/m². 300 × 300 × 10 mm tiles with 3 mm joints take about 0.32 kg/m² — around ten times less than the pennies.

Adhesive and trowel for mosaics

The trowel follows the size of one piece, not the sheet. Pieces under 100 mm take a 4 mm notch at about 1.5 kg/m²; large loose hexagons step up to the notch their size calls for, as in the tile adhesive calculator. White adhesive is common under glass and pale mosaics.

Frequently asked questions

How many mosaic sheets per m²?

About 11: a 300 × 300 mm sheet covers 0.091 m² with 2 mm joints, so 10 m² takes 110 sheets before waste and about 121 with 10%.

How much grout for penny round mosaic?

Roughly 2.5 to 4 kg/m² at 6 mm deep — about ten times as much as 300 × 300 mm tiles. It depends on the spacing and on whether the pennies are staggered or on a square grid.

How do you measure hexagon tiles?

Across the flats, from one side to the opposite side. If the size on the box is point to point, the calculator converts it with √3/2.

Do mosaics need a different adhesive?

Not a different product, but a smaller notch — usually 4 mm for pieces under 100 mm — and often white adhesive under glass or pale colours.

Does it work for large hexagon tiles?

Yes. Choose a loose 200 or 250 mm hexagon, or enter any size: pieces are counted as √3/2 × (s + j)² each, with 15% waste for the angled cuts.

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Last updated 19 October 2026

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