How to measure for tile
Measure the floor or wall in feet and multiply length by width. For a bathroom floor, measure wall to wall and subtract only large fixed items that tile will not go under, such as a built-in tub or vanity cabinet you are keeping. For a shower or backsplash, add up each wall as its own rectangle and enter the total area. Round up rather than down: running out halfway through is worse than having a few spare tiles, and later boxes may come from a different dye lot.
Worked example: a 10 × 10 ft floor in 12 × 12 tile
These are the calculator’s defaults: 12 × 12 in tile, 3/8 in thick, a 1/8 in grout joint, a straight layout, 10 tiles per box, a 1/4 × 1/4 in trowel and $3 per sq ft.
| Item | Calculation | Result |
|---|---|---|
| Area with 10% waste | 100 × 1.10 | 110 sq ft |
| Space per tile (incl. joint) | 12.125 × 12.125 ÷ 144 | 1.021 sq ft |
| Tiles | 110 ÷ 1.021 = 107.7, round up | 108 tiles |
| Boxes | 108 ÷ 10 = 10.8, round up | 11 boxes |
| Thinset | 100 ÷ 90 sq ft per bag | 2 × 50 lb bags |
| Grout | 100 × 1.125 cu in × 0.0608 lb × 1.1 | 7.5 lb → 1 × 25 lb bag |
| Materials | $330 tile + $40–$80 thinset + $15–$30 grout | $385 – $440 |
For comparison, the national installed price of $10–$50 per sq ft puts a professional job for the same floor at $1,000–$5,000, including materials and labor.
Why tile size changes everything
Small tiles mean far more grout. The grout joint volume per square foot is 144 × (L + W) ÷ (L × W) × joint width × tile thickness. A 12 × 12 tile has 24 in of joint edge per square foot of tile; a 3 × 6 subway tile has 72 in, three times as much. With the same 1/8 in joint and 3/8 in thickness, subway tile needs 3.375 cu in of grout per sq ft against 1.125 for 12 × 12. A wider joint scales grout in direct proportion, so going from 1/8 in to 1/4 in doubles it.
Large tiles go the other way on thinset. Tiles with a side of 15 in or more (12 × 24, 24 × 24 and 6 × 24 planks) need a bigger trowel notch to get full contact, and often back-buttering. Coverage drops from about 90 sq ft per bag with a 1/4 × 1/4 in notch to about 63 with 1/4 × 3/8 in and roughly 45 with a 1/2 in notch.
Choosing a layout
- Straight or offset (10% waste): the fastest to lay and the least waste. For rectangular tile, keep offsets at one-third or less on large formats to limit lippage from tile bow.
- Diagonal (15% waste): every edge piece is a triangle cut, which adds waste and labor. It can make a small room feel wider.
- Herringbone (20% waste): needs rectangular tile such as subway or plank and a careful starting line. Expect it to take noticeably longer than a straight lay.
The layout table shows tiles and boxes for each pattern so you can see the difference before you order.
DIY or hire a pro?
A small, square floor with 12 × 12 tile is a reasonable first tiling project if you rent a wet saw and take your time on layout. Showers (waterproofing), large-format tile (flatness and lippage), natural stone, and herringbone are where professionals earn their fee. Floors that flex will crack tile and grout, so check that the subfloor meets the tile maker’s deflection requirements before you start.
What’s not included
Cement backer board or an uncoupling membrane, waterproofing for wet areas, trim and bullnose pieces, transition strips, grout sealer, leveling clips, and tool rental. Thinset and grout prices are editorial estimates; specialty mortars for large-format or glass tile and epoxy grout cost more. Planning a full bathroom? The remodel budget calculator helps rough out the rest, and the flooring calculator compares tile with LVP and other floors.
How this calculator works
- Tiles = area × (1 + waste %) ÷ ((L + joint) × (W + joint) ÷ 144), rounded up. Boxes = tiles ÷ tiles per box, rounded up.
- Tile cost = boxes × tiles per box × tile face area × price per sq ft, because you pay for every tile in every box.
- Thinset bags = area ÷ coverage per bag for the selected trowel, rounded up.
- Grout volume per sq ft (cu in) = 144 × (L + W) ÷ (L × W) × joint width × tile thickness. Weight = volume × 0.0608 lb per cu in × 1.1, rounded up to 25 lb bags.
Assumptions and limitations
- Each tile is counted with one grout joint on two sides, so the tile count reflects the floor area a tile actually occupies.
- Waste is 10% for straight or offset layouts, 15% for diagonal and 20% for herringbone unless you set a custom value.
- Thinset coverage uses manufacturer figures for 50 lb bags of standard thinset (90 sq ft with a 1/4 × 1/4 in notch, 63 sq ft with 1/4 × 3/8 in). The 1/2 in figure of about 45 sq ft is an editorial estimate.
- Grout weight is an engineering estimate: joint volume × about 105 lb per cu ft for mixed sanded grout, plus 10% overage. Check the grout maker's chart for your product.
- Thinset ($20–$40 per bag) and grout ($15–$30 per 25 lb bag) prices are editorial estimates. Backer board, membrane, trim pieces, sealer and tools are not included.
These results are planning estimates, not quotes. Local prices, site conditions and building codes vary, so get written estimates from licensed contractors before you commit to a budget.
Frequently asked questions
- How many extra tiles should I buy?
- About 10% for a straight lay, 15% for diagonal and 20% for herringbone. Buy all boxes from the same lot and keep a few spare tiles for future repairs; matching a discontinued tile later is often impossible.
- Which trowel size do I need?
- As a rule of thumb, 1/4 × 1/4 in square notch for tile up to about 8 in, 1/4 × 3/8 or 1/2 in for 12 in tile, and 1/2 in for large-format tile with a side of 15 in or more. Pull up a tile after setting it: you want nearly full coverage on floors.
- Sanded or unsanded grout?
- Use sanded grout for joints 1/8 in and wider and unsanded for joints narrower than 1/8 in. Polished stone and some glass tile need unsanded or specialty grout to avoid scratching.
Sources and data
- Flooring Clarity — porcelain vs ceramic tile
- HomeGuide (2026) — tile installation cost
- Custom Building Products (CustomBlend) — customblend economical non modified thin set mortar
Prices are US national ranges reviewed October 2026. A few values are editorial estimates where no single published source exists; theCost Index marks each one. Read our methodology and editorial policy.