Calculate tile count, thinset and grout quantities — with a live HTML5 Canvas grid visualizer showing exactly how tiles lay out across your floor or wall, in metric and imperial units.
What Your Results Mean
Start by measuring your tile's actual face dimensions — not the nominal size. A "12-inch" ceramic tile often measures 11-3/4 inches, and a "24-inch" porcelain plank might actually be 23-1/2. Use the true face size; the calculator adds the grout gap separately. If you're unsure, lay a few tiles on the floor with spacers and measure the combined width to verify.
For the grout gap, 1/8 inch is the residential standard for ceramic and porcelain. Smaller gaps (1/16") require rectified porcelain tiles with precisely cut edges and unsanded grout. Larger gaps (3/16" or 1/4") are common for natural stone and require sanded grout to prevent shrinkage cracking. The gap directly affects how many tiles fit and how much grout you need.
Waste factor is critical for tile because of cuts, breakage, and pattern matching. Ten percent is the standard minimum for straight-lay patterns. Fifteen percent is recommended for diagonal (45-degree) layouts, where every perimeter tile needs to be cut. Twenty percent or more is appropriate for herringbone, chevron, or Versailles patterns where waste is inherent to the design.
Reading the Visualizer
The Canvas visualization shows the actual tile layout to scale, with each tile drawn in cream and grout joints in orange. Tiles along the perimeter are clipped to the room boundary — this is exactly what happens in real installations, where partial tiles fill in against the walls. Use the visualizer to confirm that your chosen tile size produces a layout you find aesthetically acceptable (some layouts produce ugly slivers along one wall — you may want to adjust your starting point or grout line).
Choosing the Right Thinset
Not all thinsets are created equal. Standard unmodified thinset (ANSI A118.1 in North America; class C1 under EN 12004 in Europe) is fine for ceramic tile on cement board or poured concrete. Modified thinset (ANSI A118.4 / EN 12004 class C2) adds polymers for flexibility and bond strength — required for porcelain, large-format tile (any side over 400 mm), and any installation over plywood or waterproofing membranes. For natural stone, use a white thinset to prevent color bleed-through. Coverage varies: about 7 m² per 20 kg bag with a 6 mm notch, 4 m² per bag with a 12 mm notch for large-format tile.
Pro Tip
Back-butter large-format tiles (400 mm or larger on any side) with a thin layer of thinset in addition to the troweled floor. This achieves the 95% coverage recommended by tile industry standards (the TCNA Handbook in North America) and eliminates hollow spots that lead to cracking.
The Math Behind the Calculator
Tile estimating starts with effective tile size — the tile plus its share of the grout gap. Two tiles laid side by side share one gap, so each tile "owns" half a gap on each side, totaling one full gap per tile:
effective_tile_length = tile_length + grout_gap
effective_tile_width = tile_width + grout_gap
tiles_along_room_length = ceil(room_length / effective_tile_length)
tiles_along_room_width = ceil(room_width / effective_tile_width)
base_tiles = tiles_along_room_length × tiles_along_room_width
tiles_needed = ceil(base_tiles × (1 + waste% / 100))
Thinset Coverage
Thinset coverage depends on trowel notch size, which depends on tile size:
- 5 mm V-notch — mosaics and tile up to 100 mm. Covers ~12 m² per 20 kg bag.
- 6 mm square notch — tile 100 to 380 mm. Covers ~7 m² per bag. The residential default.
- 12 mm square notch — large-format tile 380 mm+. Covers ~4 m² per bag.
This calculator uses 7 m² per 20 kg bag (the 6 mm notch default). For large-format tile, expect to buy roughly double the thinset.
Grout Coverage
Grout coverage depends on tile size, gap width, and tile depth. The general formula is:
grout_volume = (tile_length + tile_width) × gap_width × tile_depth
grout_per_tile = grout_volume / (tile_length × tile_width)
total_grout = grout_per_tile × area (all dimensions in one unit)
In practice, one kilogram of grout covers approximately 5 square metres for a standard 3 mm gap with 300 mm tile. Smaller tiles (more joints per square metre) consume more grout; larger tiles consume less. The calculator works at roughly 0.2 kg per square metre — the same rule in metric — which works well for 200 to 400 mm tiles with 3 mm gaps.
Assumptions & Limitations
Every number above rests on these constants. If your project differs, change the matching input — or read the linked guide for the full reasoning.
- Thinset: 7 m² per 20 kg bag for typical trowel sizes
- Grout: about 1 kg per 5 m² at standard joints (varies with tile size)
- 10% waste for grid layouts; add more for diagonal or herringbone
- Boxes are counted whole — always rounded up
Worked Example: 3.6 × 3 m Bathroom Floor with 300 × 300 mm Tile
A typical small bathroom: 3.6 m by 3.0 m (10.8 m²), 300 mm square porcelain tile, 3 mm grout gap, 10% waste. Here's the breakdown:
- Effective tile size: 300 + 3 = 303 mm.
- Tiles along the 3.6 m wall: ceil(3600 / 303) = 12 tiles.
- Tiles along the 3.0 m wall: ceil(3000 / 303) = 10 tiles.
- Base tiles: 12 × 10 = 120 tiles.
- With 10% waste: 120 × 1.10 = 132 tiles.
- Thinset: 10.8 m² ÷ 7 = 1.5 → 2 bags (20 kg each).
- Grout: 10.8 m² at about 0.2 kg per m² = 2.2 kg — the calculator rounds up to 5 lb (about 2.3 kg).
- Order summary: 132 tiles (11 boxes of 12), 2 bags of thinset and about 2.3 kg of grout — the complete setting kit for this floor.
If you switched to a herringbone pattern, you'd set waste to 20% — bringing the tile count to 144. If you upsized to 600 × 600 mm porcelain, you'd need only 30 base tiles (6 × 5) but would require a 12 mm notch trowel, pushing thinset to 3 bags. The calculator adjusts instantly when you change inputs.
Reminder
The estimate excludes waterproofing membrane, cement board if going over wood subfloor, sealer for natural stone, transition strips and labour. Membrane and backer board are separate line items — plan them before you start, especially in wet areas.
