Tile Calculator — How Many Tiles Do I Need?
Enter your room dimensions and tile size to find how many tiles to buy. Includes grout joint width, waste factor, and box count. Always add at least 10% extra for cuts and future repairs.
Always add 10–15% extra for cuts and waste. Box quantities vary by manufacturer — verify tiles per box before ordering.
How to Calculate Tile Quantity
The basic formula is room area divided by tile area, rounded up, with a waste percentage added. When grout joints are factored in, each tile occupies slightly more than its face dimensions.
Tile Calculation Formula
Floor area (sq ft) = Room length × Room width Tile area (sq ft) = (Tile width + Grout width) × (Tile height + Grout width) ÷ 144 Tiles needed = ceil(Floor area ÷ Tile area) × (1 + Waste%) Boxes needed = ceil(Tiles needed ÷ Tiles per box)
Example: 10 ft × 12 ft room, 18×18 in tiles, 3/16" grout, 10% waste:
Floor area = 10 × 12 = 120 sq ft
Tile cell = (18 + 0.1875) × (18 + 0.1875) = 18.1875 × 18.1875 = 330.78 sq in
= 330.78 ÷ 144 = 2.297 sq ft
Tiles (raw) = 120 ÷ 2.297 = 52.2 → 53 tiles
+ 10% waste = 53 × 1.10 = 58.3 → 59 tiles
Boxes = ceil(59 ÷ 12) = 5 boxes Tile Types and Best Uses
| Tile Type | Water Resistance | Best Use | Cost Range |
|---|---|---|---|
| Ceramic | Moderate | Wall, low-traffic floor | $0.50–$5/sq ft |
| Porcelain | Very high (<0.5% absorption) | Floor, wet areas, outdoor | $1–$15/sq ft |
| Natural Stone (marble, slate) | Low (needs sealing) | Accent walls, luxury floors | $5–$30/sq ft |
| Glass | 100% (non-porous) | Backsplash, shower walls | $7–$30/sq ft |
| Mosaic (<6" tiles) | Varies by material | Accent, shower floor | $5–$25/sq ft |
Installation Patterns and Waste
The installation pattern significantly affects how much waste you generate:
- Grid (straight stacked): 5% waste. Tiles align edge-to-edge horizontally and vertically. Fastest to install, fewest cuts.
- Brick / offset (running bond): 10% waste. Alternate rows offset by half a tile width, like brickwork. Standard for subway tile.
- Diagonal (45°): 15% waste. Tiles rotated 45° produce diagonal cut lines at every wall. Visually enlarges small rooms but wastes significantly more material.
- Herringbone: 15–20% waste. Rectangular tiles set in a V pattern. Requires many cuts and careful planning.
- Versailles / random pattern: 10–15% waste. Multiple tile sizes arranged in a repeating larger pattern. Requires careful layout planning.
Substrate and Surface Preparation
Tile requires a rigid, flat substrate. Any flex in the substrate causes grout to crack and tiles to loosen over time. Standard preparation:
- Concrete slab: Ideal substrate — grind high spots, fill cracks with floor leveler.
- Plywood subfloor: Must be at minimum 1-1/8" total thickness. Add 1/4" cement backer board (HardieBacker, Durock) for wet areas.
- Existing ceramic tile: Can tile directly over existing tile if it is firmly bonded, flat, and grout joints are filled. Check that the added height clears transitions and appliances.
- Drywall: Only acceptable for wall tile in dry areas. Wet areas (shower, tub surround) require cement board or moisture-resistant greenboard.
Grout Types
| Grout Type | Joint Width | Characteristics |
|---|---|---|
| Unsanded | 1/16"–1/8" | For small joints; use on polished stone (sanded scratches) |
| Sanded | 1/8"–1/2" | Most common; for standard floor/wall joints |
| Epoxy | 1/16" and up | Chemical-resistant, stain-proof; used in commercial kitchens |
| Furan resin | 1/4" and up | Extreme chemical resistance; industrial use |
Frequently Asked Questions
How many 12×12 tiles do I need for a 10×12 room?
A 10×12 room is 120 sq ft. A 12×12 inch tile covers exactly 1 sq ft. With a 1/8" grout joint, each tile+grout cell is 12.125"×12.125" = 147.02 sq in = 1.021 sq ft. You need 120 ÷ 1.021 = 117.5, so 118 tiles before waste. With 10% waste: 118 × 1.10 = 130 tiles. At 12 tiles per box, that is 11 boxes.
What waste percentage should I use?
Use 5% for straight grid layouts in rectangular rooms with no obstacles. Use 10% for most standard installations — this accounts for cuts at walls and corners. Use 15% for diagonal (45°) layouts, herringbone, or any pattern where every edge tile must be cut at an angle. Add another 5% if the room has many obstacles (columns, fixtures) or irregular walls. Always save leftover tiles for future repairs.
How do I calculate grout quantity?
Grout quantity depends on tile size and grout joint width. A standard rule: for 12×12 tiles with a 3/16" joint, you need approximately 0.33 lbs of sanded grout per sq ft. For smaller tiles (4×4) with 1/8" joints, expect 0.6–0.8 lbs/sq ft. Most grout bags list square footage coverage — check the label. Add 10% extra for the same reason as tile waste.
What is the difference between floor tile and wall tile?
Floor tile must have a slip-resistance rating (COF — Coefficient of Friction). For wet areas (shower floors), COF must be ≥ 0.60. Wall tile does not bear weight so can be thinner and lighter, but it must be able to accept the adhesive. Porosity also matters: wall tiles are often more porous (and thus more absorbent). In wet areas, all tiles should have a low water absorption rating (< 3% for porcelain). Never use wall-only tile on a floor.
Should I tile before or after installing cabinets?
Most professionals tile the floor first, then install cabinets on top of the tile. This provides a perfectly level base for cabinets and means you never have to tile around toe-kicks. However, this uses more tile since you tile the area under the cabinets. For kitchen renovations where cabinets will stay in place for 20+ years, this is the correct approach. For bathroom vanities, tiling to the vanity edge is acceptable since vanities are replaced more frequently.
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