ToolwickTile & Flooring Coverage Calculator
Use this tile calculator to find out how many tiles you need, how much waste to buy, how many boxes to order, and your total cost — for any room size.
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Results
How to Use This Tile Calculator
Enter your room's length and width in your preferred unit (feet, meters, or inches), then enter the individual tile dimensions. Set a waste percentage using the slider — 10% is standard for straight-lay patterns, 15% for diagonal, and up to 30% for complex cuts or irregular rooms. Optionally add tiles-per-box, price-per-box, and grout joint width to get full cost estimates. Hit Calculate Tiles and this tile calculator instantly shows your complete breakdown.
Use the Multiple Rooms tab to sum up totals across a kitchen, bathrooms, and hallways in one shot. Both tabs use the exact same math, including grout joint width, so results stay consistent whichever way you enter a room.
Why This Matters
Buying too few tiles means a costly second trip to the store — and there's no guarantee the same batch will match (tiles are manufactured in dye lots, and color variation between batches is real). Buy too many and you've wasted money on materials you'll store in a garage forever.
Take a 12 ft × 12 ft bathroom floor: 144 sq ft of floor space. With 12"×12" tiles, a standard 1/8" grout joint, and a 10% waste factor, this calculator says you need 156 tiles. At 10 tiles per box, that's 16 boxes — and at $35 a box, a $560 purchase. Switch that same room to a diagonal layout and bump waste to 15%: you now need 163 tiles, which still rounds up to 17 boxes — just one extra box, about $35 more. Small percentage changes can nudge you into an extra box, so it pays to check the math rather than guess. A kitchen with an island or L-shaped cuts should use 20%+ waste to account for the extra trimming around corners and obstacles.
How It's Calculated
The calculation follows these steps:
- Room Area = Length × Width (converted to sq ft or sq m consistently)
- Effective Tile Size = (Tile Length + Grout Joint) × (Tile Width + Grout Joint) — grout is added to each tile's footprint
- Base Tile Count = Room Area ÷ Effective Tile Area
- Tiles With Waste = Base Count × (1 + Waste% ÷ 100), rounded up to the next whole tile
- Boxes Needed = Tiles With Waste ÷ Tiles Per Box, rounded up to the next whole box
- Total Cost = Boxes Needed × Price Per Box
All units are converted to inches internally before computing areas, so mixing feet, meters, and inches across fields is safe.
Worked Example
Say you're tiling a 12 ft × 10 ft room with 12"×12" tiles, a 1/8" (0.125 in) grout joint, 10 tiles per box at $35 per box, and the standard 10% waste factor. Here's what the calculator does step by step:
- Room area: 12 ft × 10 ft = 120 sq ft (17,280 sq in).
- Effective tile size: 12" + 0.125" = 12.125" per side, so each tile (with its grout allowance) covers 12.125 × 12.125 = 147.02 sq in.
- Base tile count: 17,280 ÷ 147.02 ≈ 117.5 tiles, rounded up to 118 tiles before waste.
- Add 10% waste: 117.5 × 1.10 ≈ 129.3, rounded up to 130 tiles to buy.
- Boxes needed: 130 ÷ 10 tiles per box = 13 boxes exactly.
- Total cost: 13 boxes × $35 = $455.
Plug those same numbers into the calculator above and you'll see this exact result — 130 tiles, 13 boxes, $455.
Tips & Common Mistakes
- Always round boxes UP — you can never buy half a box, and stopping mid-job because you're 3 tiles short is frustrating.
- Match dye lots — buy all tiles at once, and keep 5–10% extra in storage for future repairs.
- Measure twice — for L-shaped or irregular rooms, break the space into rectangles and calculate each separately using the Multi-Room tab.
- Account for obstacles — islands, columns, bathtubs, and fireplaces reduce your floor area. Subtract those footprints from the room area before calculating.
- Grout joint size matters — a 3/16" joint on 12"×24" tiles adds a few extra tiles across a large room. Always include it, and enter the same grout width in both tabs so your totals stay consistent.
Frequently Asked Questions
How much waste percentage should I use?
Use 10% for standard straight-lay patterns in regular rectangular rooms. Go to 15% for diagonal or herringbone patterns, and 20–30% for complex rooms with many cuts, L-shapes, or curves. If you're a beginner tiler, add an extra 5% to account for mistakes during cutting.
Should I include grout joint width in my calculation?
Yes, and this calculator does it automatically in both the Single Room and Multiple Rooms tabs. A 1/8" grout joint on a 12"×12" tile increases the effective tile footprint slightly — across hundreds of tiles, this adds up. Ignoring grout can cause you to buy several extra tiles you don't actually need.
What if my room is not a perfect rectangle?
Break the room into rectangular sections and use the Multiple Rooms tab — one entry per rectangle. Add up all sections to get total tiles and cost. This works well for L-shaped rooms, rooms with closets, and open-plan spaces.
Can I use this for wall tiles too?
Absolutely. The same square-footage math applies. Enter your wall height as "length" and wall width as "width." For a backsplash, use the exact dimensions of the backsplash area. Just subtract any windows or outlets from the area if they're large enough to matter.
Why do the Single Room and Multiple Rooms tabs give slightly different numbers for the same room?
They shouldn't, as long as you enter the same grout joint width in both tabs. Both tabs factor grout spacing into the tile footprint identically, so a single room entered in either tab will produce the same tile count and box count.
How many boxes of tile should I buy?
Divide your total tiles needed (including waste) by the tiles per box, then always round up to the next whole box. You can't buy a fraction of a box, and it's better to have a couple of leftover tiles for future repairs than to run short mid-project.