How Much Tile Do I Need?

For a 10 × 12 ft floor (120 sq ft) with a straight grid layout, plan on about 132 sq ft of tile after 10% waste — that’s 9 boxes at the standard 15 sq ft per box of 12×12 inch tile.

That box count, not the raw square footage, is the number you actually hand to the supplier. Getting there is three steps: measure the room, add a waste percentage set by your layout pattern, then divide by how much a single box covers and round up.

Boxes are the real unit, and coverage varies by tile size

Tile is priced and boxed by the manufacturer, and box coverage depends entirely on tile size. A box of standard 12×12 inch tile holds about 15 tiles and covers roughly 15 sq ft, since each tile is exactly 1 sq ft. Larger-format tile covers more square footage per box with fewer pieces; mosaics and small-format tile cover far less per box because so much of the box is packaging and sheet backing rather than tile face. Always check the coverage number printed on the box you’re actually buying — the 15 sq ft figure is a 12×12 inch baseline, not a universal constant. The tile calculator takes tile size as an input and adjusts box coverage accordingly.

Square footage: length times width, minus what won’t be tiled

Measure the room’s length and width in feet and multiply them to get square footage — a 10 ft by 12 ft floor is 120 sq ft. Subtract large fixed obstructions that won’t be tiled, like a permanent island base or a tub apron; leave doorways and pass-throughs in the total, since tile generally runs through them rather than stopping at the frame. That square footage is the exact number the tile calculator asks for, and it’s the base every other number in this article is built from.

Waste percentage is set by the layout, not a flat rule

Waste isn’t a single number — it’s tied to how the tile is laid, because more complex patterns mean more cuts and more broken pieces:

Layout	Waste
Straight / grid	10%
Diagonal (45°)	15%
Herringbone / complex	20%

A straight grid lay only needs cuts at the room’s edges, so 10% covers it. A diagonal lay cuts every tile at a 45-degree angle against square walls, which wastes noticeably more material. Herringbone and other interlocking patterns cut nearly every piece, which is why they sit at 20%. Pick the layout first — it changes the box count more than almost any other variable in the job.

Backsplashes: same math, measured wall to wall

A backsplash uses the identical square-footage-plus-waste-plus-box-coverage method, just on a wall instead of a floor: multiply width by height instead of length by width. Backsplash tile is typically sold as 3×6 inch subway tile in boxes of about 100 tiles, covering roughly 12.5 sq ft per box — noticeably less than a 12-inch floor tile box, so don’t reuse the 15 sq ft figure here. A 10 ft wide by 2 ft tall backsplash is 20 sq ft; add 10% waste for a straight/stacked layout and that’s about 22 sq ft, which rounds up to 2 boxes. Backsplash waste follows the same 10/15/20% tiers as floor tile, but real-world jobs often land on the higher end regardless of the chosen pattern, since outlets, switches, and corner returns force extra cuts that a plain floor doesn’t have. The backsplash calculator takes width and height directly rather than requiring the length/width conversion by hand.

Grout and thinset scale off the same square footage, in bags

Once the tile count is set, grout and thinset mortar are sized from the same tiled square footage, but they’re sold by weight, not by area, so their coverage-per-unit numbers look nothing like the tile box figure. A 25 lb bag of sanded grout covers about 110 sq ft on standard 12-inch tile with 1/8-inch joints, at 10% waste. That figure drops fast with smaller tile or wider joints — either one can cut real coverage to a third of the baseline, since more linear feet of joint (or wider joints) means more grout per square foot regardless of the tile face area. A 50 lb bag of thinset mortar covers about 95 sq ft with a standard 1/4-inch square-notch trowel, also at 10% waste; a bigger notch size or large-format tile (16 inches and up) needs more mortar for full contact and can cut real coverage to 50–70 sq ft per bag. Use the grout calculator and thinset calculator with your actual tile size and joint width rather than assuming the 12-inch/1/8-inch baseline applies.

Putting it together: one floor, three materials

For the 10 × 12 ft (120 sq ft) straight-lay floor from the top of this article, all three material counts land on the same 132 sq ft waste-adjusted total, divided by three different box/bag coverage rates:

Material	Coverage per unit	Boxes/bags needed
Tile (12×12 in.)	~15 sq ft/box	9 boxes
Grout (25 lb bag)	~110 sq ft/bag	2 bags
Thinset (50 lb bag)	~95 sq ft/bag	2 bags

Same square footage, same 10% waste margin, three separate purchase counts — which is exactly why a tile job needs three calculator runs, not one.

What it costs (2026 ballpark)

Materials only, before labor, US national ballpark as of 2026-07 — actual pricing swings with material grade (ceramic vs. porcelain vs. natural stone) and region:

• Tile: roughly $25–80 per box, $45 typical.
• Backsplash tile: roughly $18–60 per box, $32 typical.
• Grout: roughly $12–35 per bag, $20 typical.
• Thinset: roughly $14–38 per bag, $22 typical.

For the 10 × 12 ft floor above (9 boxes of tile, 2 bags of grout, 2 bags of thinset), that works out to roughly $280–$870 in materials, with $490 as a reasonable middle estimate. Run your own room’s numbers through the tile, grout, and thinset calculators for a cost range built on your actual square footage and layout rather than this worked example.

Updated: 2026-07-15