Tile laying calculator

DIY complexity

Advanced

Achieving a level, evenly spaced tile layout with clean cuts takes real practice, and wet-area work (showers, bathroom floors) adds waterproofing membrane work that is unforgiving of mistakes.

Introduction

This calculator estimates the number of ceramic or porcelain tiles needed to cover a floor or wall, along with the adhesive, grout and waterproofing quantities that go with the installation. It works from the room dimensions you measure and the face size of the tile you have chosen, because the number of pieces required depends entirely on how much surface a single tile actually covers. Supported project types include bathroom and kitchen floors, wet-room walls, hallways and general living-space tiling, in straight, diagonal or offset patterns — each pattern changes how much cutting waste to expect. For wet areas such as showers and bathroom floors, the tool can add a waterproofing membrane allowance on top of the tile count, since these zones need tanking before tiles go down. Results are given in whole tiles after your chosen waste percentage, plus adhesive coverage per square metre and grout volume based on joint width and tile thickness. The calculator cannot verify substrate flatness, falls to drain, or structural suitability for large-format tiles, and it does not replace a tiler's on-site survey for complex layouts or mixed-size patterns.

Quick answer

For a 3 × 2 m wet-area bathroom floor (6 m²) with 600 × 300 mm tiles and 15% cutting waste, the theoretical requirement is 6 × 1.15 = 6.9 m², which needs ceil(6.9 ÷ 0.18) = 39 tiles at 0.18 m² per tile.

Calculation methodology

01Measure the room's floor or wall area, and subtract fixed fixtures such as a bath, kitchen island or built-in unit that will not be tiled.
02Calculate the face area of one tile from its length and width, and confirm whether the pattern is straight, diagonal or an offset/brick bond.
03Add the pattern-related cutting waste — diagonal and offset layouts consume more part-tiles at the edges than a straight grid.
04Divide the net area including waste by the tile face area and round up to whole tiles, since a fraction of a tile cannot be purchased.
05For wet areas, add a waterproofing membrane allowance sized to the same net area, typically with its own overlap and pond/upstand allowance.
06Calculate adhesive quantity from coverage rate per square metre and bag size, and grout volume from joint width, tile thickness and tile dimensions.

Formulas

tiles = ceil(net_area × (1 + waste) ÷ tile_area)

The net tileable area is inflated by the waste percentage to absorb cuts, then divided by the face area of a single tile, and rounded up because tiles can only be bought whole.

Variables

net_area = room area minus fixed exclusions (m²)
waste = cutting allowance for the chosen pattern (%)
tile_area = tile length × tile width (m²)
tiles = whole tiles to purchase

Rounding rule: Always rounded up (ceiling) to the next whole tile; some suppliers additionally sell only in full boxes, which adds a second rounding step.

Limitation: Assumes a single tile size across the whole area; mixed formats, borders or feature strips must be calculated as separate zones.

adhesive_bags = ceil((net_area × coverage_kg_per_m2) ÷ bag_size); grout_volume = joint_length × joint_width × tile_thickness

Adhesive quantity comes from the trowel coverage rate stated by the manufacturer, multiplied by the tiled area and divided by bag size. Grout volume comes from the total length of joints in the layout, multiplied by the joint width and tile thickness.

Variables

coverage_kg_per_m2 = adhesive consumption per m² for the chosen trowel notch (kg/m²)
bag_size = adhesive bag weight (kg)
joint_length = total linear metres of grout joints in the layout (m)
joint_width = gap between tiles (mm)
tile_thickness = tile depth (mm)

Rounding rule: Adhesive bags are rounded up to whole bags; grout is typically rounded up to whole packs sold by the manufacturer in kg or litre units.

Limitation: Coverage rates vary with substrate flatness, trowel notch size and tile back-buttering practice — use the figure from the selected adhesive's technical data sheet, not a generic average.

Inputs that matter

Tile face sizeDirectly sets the tile area used to divide the net surface; a small measurement error compounds across every tile in the count.
Laying patternDiagonal and offset layouts create more part-tiles at walls and corners than a straight grid, so they need a higher waste allowance.
Wet-area flagSwitches on the waterproofing membrane allowance, which showers and bathroom floors need before tiling but a hallway does not.
Joint widthWider joints increase both grout volume and, on large areas, the effective coverage per tile, subtly changing the tile count.
Fixed exclusions (bath, island, cabinets)Reduces the net tileable area; forgetting them causes systematic over-ordering on every job.
Waste percentageAbsorbs breakage, cutting at edges and pattern-matching losses — complex layouts and small rooms with many cuts need more than a simple large rectangular room.

Worked examples

Bathroom floor, wet-area waterproofing

A 3 × 2 m bathroom floor (6 m²), 600 × 300 mm tiles (0.18 m² each), straight pattern, wet-area waterproofing enabled, 15% waste.

net_area = 6 m². With 15% waste: 6 × 1.15 = 6.9 m². tiles = ceil(6.9 ÷ 0.18) = ceil(38.33) = 39 tiles. Waterproofing membrane allowance is also sized to 6 m² plus its own overlap.

6 m² is the measured floor, 6.9 m² is the requirement with waste, and 39 tiles is the final purchase quantity — 0.12 m² of surplus tile is normal and useful as spares for future repairs.

⚠ 15% waste is an editable example for a small wet room with many cuts around fixtures — a larger, more open floor typically needs less.

Kitchen floor with an island, diagonal pattern

A 4 × 3 m kitchen floor (12 m²) with a fixed island footprint of 0.8 × 0.6 m (0.48 m²) excluded, 600 × 600 mm tiles (0.36 m² each), diagonal pattern, 20% waste.

net_area = 12 − 0.48 = 11.52 m². With 20% waste for the diagonal pattern: 11.52 × 1.20 = 13.824 m². tiles = ceil(13.824 ÷ 0.36) = ceil(38.4) = 39 tiles.

11.52 m² is the theoretical net area after excluding the island, 13.824 m² is the requirement including diagonal waste, and 39 tiles is the final purchase figure. The higher waste percentage versus a straight pattern reflects the extra angled cuts along every wall.

⚠ Excluding the island footprint only accounts for its base area — skirting-level trim cuts around its edges still consume tiles and should stay inside the waste allowance, not be treated as fully avoided material.

Living room floor with boxes, adhesive and grout

A 6 × 5 m living room floor (30 m²), 600 × 600 mm tiles (0.36 m² each) sold 8 per box, straight pattern, 10% waste, adhesive coverage 4 kg/m² sold in 20 kg bags.

net_area = 30 m². With 10% waste: 30 × 1.10 = 33 m². tiles = ceil(33 ÷ 0.36) = ceil(91.67) = 92 tiles → boxes = ceil(92 ÷ 8) = 12 boxes (96 tiles, 4 surplus). Adhesive: 30 × 4 = 120 kg → bags = ceil(120 ÷ 20) = 6 bags.

The tile count (92) and the box-rounded purchase quantity (96) differ because boxes are a fixed pack size; the 4 extra tiles are a normal consequence of buying whole boxes, not an error. Adhesive at 6 bags is calculated independently from the tile count, using the tiled area directly.

⚠ 4 kg/m² is an editable example coverage rate — actual adhesive consumption depends on trowel notch size and substrate flatness, and must come from the selected product's data sheet, not a generic figure.

Reading the results

The result panel separates the net tileable area you measured, the requirement including waste, and the final whole-tile (and where applicable whole-box) purchase quantity — each figure grows for a specific reason rather than by rounding inconsistency. Purchase quantity exceeds the theoretical requirement because tiles, boxes and bags are sold in fixed units, and because a small surplus of tiles is genuinely useful as spares for future repairs of the same batch. Adhesive, grout and waterproofing quantities are shown as separate line items because they follow different coverage rates and packaging sizes than the tile count itself.

Common mistakes

Using the tile's nominal or box label size instead of its actual measured face dimensions, which can differ by a few millimetres and skew the count on large areas.
Forgetting to subtract fixed fixtures such as a bath, kitchen island or built-in cabinet run from the tileable area.
Applying the same waste percentage to a diagonal or offset pattern as to a straight layout, which understates real cutting losses.
Skipping the waterproofing membrane allowance in a shower or wet room because it is easy to think of as a separate purchase from the tiling job.
Confusing adhesive coverage per bag with coverage per square metre — the two numbers are related but not interchangeable in the calculation.
Assuming grout joint width has no effect on quantities; wider joints increase both grout volume and, on large-format tiles, the number of tiles needed to cover the same net area.

Adapting to your country

Tile sizes, packaging counts and adhesive coverage rates vary significantly by manufacturer and country — always take the face dimensions, box quantity and trowel coverage from the selected product's technical data sheet rather than a generic assumption. Metric markets size tiles in millimetres and price by the square metre or per box; imperial markets often size tiles in inches and price per square foot. Wet-area waterproofing systems and their required overlaps follow local building practice, and terminology for the same system can differ between countries. Selecting a different currency changes only the displayed symbol — enter a current local supplier price for an accurate cost estimate, and confirm applicable sales tax separately since it is not built into the calculator's output.

Limitations and verification

This calculator produces a planning estimate, not a tiler's quotation, structural assessment or building-regulation approval. It does not verify substrate flatness, floor levelness, falls to drain in wet rooms, or whether the floor structure can support large-format or natural stone tiles. Complex layouts with mixed formats, borders, mosaic inserts or curved walls should be broken into separately measured zones or verified with a tiler's on-site survey. Always confirm final quantities, adhesive coverage and waterproofing specification against the selected products' current technical data sheets before ordering.

Last reviewed: 2026-08-24

Frequently asked questions

Should I measure the tile size printed on the box or the actual tile?

Use the actual measured face dimensions where possible. Printed nominal sizes can round to the nearest 5 or 10 mm and drift slightly from the real tile, which matters more as the tiled area grows.

Why does a diagonal pattern need more waste than a straight one?

A diagonal layout creates triangular part-tiles along every wall instead of simple straight cuts, consuming more material per linear metre of edge, so its default waste allowance is set higher.

Do I need to add waterproofing separately from the tile count?

Yes. Waterproofing membrane is a different product with its own coverage rate and overlap requirement — enabling the wet-area option adds it as a separate line sized to the same net area, not folded into the tile count.

How is grout volume different from adhesive quantity?

Grout fills the joints between tiles and is calculated from joint length, width and tile thickness; adhesive bonds the tile to the substrate and is calculated from the tiled area and the trowel's coverage rate — they use unrelated formulas.

Why does the calculator round up to whole boxes as well as whole tiles?

Many suppliers sell tiles only in fixed-count boxes. The calculator first rounds up to whole tiles, then — if you provide a box size — rounds that figure up again to whole boxes, since a partial box cannot be purchased.

Should I subtract a shower tray or bathtub footprint from the floor area?

Yes, subtract the footprint of any fixture that will not be tiled underneath. Leave small pipe penetrations and drain covers within the waste allowance rather than deducting them individually.

Does changing the currency convert an entered material price?

No. Changing currency only changes the displayed symbol and formatting; enter a current local supplier price in the currency you have selected.

Is the tile count enough to place a full order without checking anything else?

No. Confirm the batch or shade number is consistent across all boxes, check substrate suitability for the tile format and weight, and verify local wet-room waterproofing requirements before ordering.

Tile calculator.

Room and dimensions

Tile and laying pattern

Technical options

How does the calculator work?

Tile quantity formula

Verified example

Frequently asked questions

Tile calculator

Project inputs

Results

Introduction

Calculation methodology

Formulas

Inputs that matter

Worked examples

Bathroom floor, wet-area waterproofing

Kitchen floor with an island, diagonal pattern

Living room floor with boxes, adhesive and grout

Reading the results

Common mistakes

Adapting to your country

Limitations and verification

Frequently asked questions

Tile calculator.

Room and dimensions

Tile and laying pattern

Technical options

How does the calculator work?

Tile quantity formula

Verified example

Frequently asked questions

Project inputs

Results

Introduction

Calculation methodology

Formulas

Inputs that matter

Worked examples

Bathroom floor, wet-area waterproofing

Kitchen floor with an island, diagonal pattern

Living room floor with boxes, adhesive and grout

Reading the results

Common mistakes

Adapting to your country

Limitations and verification

Frequently asked questions

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