How to Calculate Tiles Needed: Complete Installation Guide
Tile quantity is area divided by tile coverage, then increased for waste. This guide covers floor and wall takeoffs, grout joints, pattern layouts, waste percentages, and worked examples for rooms, showers, and backsplashes.
How to Calculate Tiles Needed
Tile jobs fail in the planning stage more often than in the setting stage. Order too few boxes and you risk a dye-lot mismatch weeks later; order far too many and you tie up money in stock you cannot return. The calculation itself is straightforward: measure the area to cover, divide by the area each tile covers, then add a waste allowance for cuts and breakage.
This guide expands that process for floors, walls, showers, and backsplashes, including how grout joints, patterns, and tile size change the count.
The basic formula
N = \fracA_\mathrmsurfaceA_\mathrmtile × (1 + w)
Where:
- N = number of tiles to order (round up to a whole tile, then to full boxes)
- A_\mathrmsurface = area to be tiled
- A_\mathrmtile = face area of one tile (use the same units)
- w = waste fraction (for example, 0.10 for 10%)
Equivalently, compute the raw count first:
N_\mathrmraw = \fracA_\mathrmsurfaceA_\mathrmtile
N_\mathrmorder = \lceil N_\mathrmraw × (1 + w) \rceil
Step 1: Measure the surface area
For a rectangular room or wall:
A = L × W
Use feet for square feet, or metres for square metres — stay consistent.
Example. A floor 12 ft by 10 ft:
A = 12 × 10 = 120\ \mathrmsq\ ft
Irregular rooms
Split the plan into rectangles (and triangles if needed), compute each area, then add:
A_\mathrmtotal = A_1 + A_2 + ·s
Subtract openings you will not tile (cabinets that stay put, large built-ins). Doorway thresholds are often tiled; closet floors usually are.
Example. Living area 14 × 12 ft plus a hallway 8 × 3 ft, minus a 3 × 2 ft island footprint that will not be tiled:
A = (14 × 12) + (8 × 3) - (3 × 2) = 168 + 24 - 6 = 186\ \mathrmsq\ ft
Walls
Wall area is height times length along the wall. For a full room:
A_\mathrmwalls = P × H - A_\mathrmopenings
Where P is the perimeter to be tiled and H is tile height. Subtract windows and doors.
Step 2: Tile area (and grout)
Nominal tile size is the marketed face size. Installed coverage per tile is slightly larger if you include the grout joint, but for ordering boxes most people use the tile face area and let the waste factor cover joint space and cuts. For a tighter estimate of coverage:
A_\mathrmmodule = (L_\mathrmtile + g)(W_\mathrmtile + g)
Where g is grout joint width (same units as tile length and width).
Example. A 12 × 12 in tile with a 1/8 in grout joint:
A_\mathrmmodule = (12.125 × 12.125)\ \mathrmin^2 = 147.0\ \mathrmin^2 = 1.021\ \mathrmsq\ ft
Without grout, the face alone is 1.0 sq ft. The difference is small for large tiles and more noticeable for mosaics and small formats.
Convert square inches to square feet by dividing by 144:
A_\mathrmsq\ ft = \fracL_\mathrmin × W_\mathrmin144
Step 3: Divide and add waste
Example — 12×12 floor tile. Room = 120 sq ft, tile = 1.0 sq ft, waste = 10%:
N_\mathrmraw = (120)/(1.0) = 120
N_\mathrmorder = 120 × 1.10 = 132\ \texttiles
If boxes contain 15 sq ft (15 tiles of this size):
\textBoxes = \lceil 132 / 15 \rceil = \lceil 8.8 \rceil = 9\ \textboxes
Worked example — metric wall
A shower wall 2.4 m wide by 2.1 m high uses 30 × 60 cm tiles. Waste 15% for a staggered layout:
A = 2.4 × 2.1 = 5.04\ \mathrmm^2
A_\mathrmtile = 0.30 × 0.60 = 0.18\ \mathrmm^2
N_\mathrmraw = (5.04)/(0.18) = 28
N_\mathrmorder = 28 × 1.15 = 32.2 arrow 33\ \texttiles
Waste percentages by situation
w = 0.10 \quad \textis the default for most residential floors
Bump waste up when tiles are large relative to the room (more cut pieces) or when the layout is diagonal.
Pattern and layout effects
Grid (straight). Lowest waste. Align joints; plan cuts at walls.
Running bond / brick. Offset by half or one-third. Slightly more cuts than grid; 10–12% waste is typical.
Diagonal. Tile edges hit walls at 45°, producing many triangular offcuts. Use about 15% waste.
Herringbone. Beautiful and cut-heavy. Plan on 15–20%, and dry-lay a section before you order the final top-up.
Sheet-mounted mosaic. Calculate from sheet coverage (for example, each sheet covers 1 sq ft), not from individual 1 in tesserae.
Backsplashes and borders
A backsplash is just a long, short wall:
A = L × H
Example. 10 ft of countertop with an 18 in (1.5 ft) splash height:
A = 10 × 1.5 = 15\ \mathrmsq\ ft
With 3×6 in subway tile (A_\mathrmtile = 18/144 = 0.125 sq ft) and 12% waste:
N = (15)/(0.125) × 1.12 = 120 × 1.12 = 134.4 arrow 135\ \texttiles
Order decorative border pieces separately — their coverage is not the same as field tile.
Floors versus walls: practical notes
- Floors: Measure wall-to-wall; decide whether to tile under movable appliances.
- Walls: Confirm tile height (full height, wainscot, or shower surround only).
- Showers: Include each wall; niches add area but also cuts — do not reduce waste.
- Outdoor: Freeze–thaw rated tile and a higher breakage allowance if cutting porcelain outdoors.
Boxes, dye lots, and extras
Always convert the tile count into full boxes, then buy one extra box when the job is large or the tile is being discontinued. Keep leftover tiles from the same dye lot (shade number on the box) for future repairs — a replaced tile from a new lot often does not match.
\textBoxes = \lceil N_\mathrmorder / N_\mathrmper\ box \rceil
Applications
Kitchen and bath remodels. Combine floor, wall, and splash takeoffs on one materials list with separate waste factors.
Commercial corridors. Long runs favor large-format tile; waste may be lower, but substrate flatness tolerances get stricter.
Accent bands and mosaics. Calculate field tile and accent materials as separate line items.
Heated floors. Area for tile equals area for heating cable planning — use the same measured square footage.
Cost planning. Labor is often bid per square foot; material count still needs the waste-adjusted tile total.
Common mistakes
Forgetting closets, niches, or the shower curb. Small surfaces add up.
Using box "coverage" without reading the label. Some coverage figures already assume a grout joint; others are face-only.
Applying only 5% waste on a diagonal layout. You will run short.
Ordering the exact mathematical count with no spare. Breakage and a bad tile in the last box are normal.
Mixing dye lots. Buy enough in one purchase for the whole contiguous area.
Measuring in mixed units. Convert tile inches and room feet into one system before dividing.
Ignoring layout starting point. A balanced layout (equal cuts on opposite walls) can change how many tiles you cut in half — dry-lay or snap chalk lines before setting.
Frequently asked questions
Should I tile under cabinets? Usually no for base cabinets that stay; yes if cabinets are removed during the remodel. Match what the design intends.
Do I need the same waste percent for walls and floors? Walls with windows, niches, and borders often need a bit more than a simple floor. Use 10% as a floor default and 12–15% for busy wet walls.
How do I handle 12×24 tiles? Same formula: A_\mathrmtile = (12 × 24)/144 = 2.0 sq ft per tile. Large rectified porcelain still needs waste for cuts — do not assume zero waste because the tile is big.
What about rectified versus pressed edges? Rectified edges allow tighter joints; that slightly changes module size but not the ordering method. Follow the manufacturer joint recommendation.
Can I return unopened boxes? Often yes within a time window; opened boxes and special orders usually cannot be returned. Still keep one spare box for repairs.
Is square footage of the room equal to tile square footage? Almost — grout and cuts mean you need more tile face area than the floor area. That is what the waste factor accounts for.
Summary
Measure the area, divide by one tile's coverage, then increase for waste:
N = \fracA_\mathrmsurfaceA_\mathrmtile × (1 + w)
Use about 10% waste for ordinary grid floors, more for diagonals and complex patterns, round up to full boxes, and keep matching extras from the same dye lot.
Plan your order with our Tile Calculator.