Tile Calculator

How the tile calculator works

A 10 × 12-ft floor — 120 sq ft — takes 132 pieces of 12×12-inch tile and about 1.4 lbs of grout. Each 12×12 tile covers exactly 1 sq ft, so a 10% waste factor turns 120 sq ft into 132 sq ft and 132 tiles. With a ⅛-inch joint and ⅜-inch-thick tile, sanded grout is the right choice.

The math is straightforward: floor area is length × width. Tile size is given in inches (or cm in metric mode), so each tile covers tile_w × tile_h in the appropriate units. Divide the total area by area-per-tile, apply the waste factor, and round up to whole tiles. Grout is estimated from the un-wasted area — you only grout the joints you actually install — using the tile's perimeter-to-area ratio, the joint width, and the tile thickness.

Tile size changes everything downstream

Size is not just a look. A bigger tile has less edge per square foot, so it needs fewer pieces, less grout, and less labor — but it is less forgiving of a floor that isn't flat, and every cut wastes more material. Here is the same 120 sq ft floor in four common sizes, using the calculator's default ⅛" joint and 10% waste:

Notice that the grout column falls by a factor of six across the table while the area stays fixed at 120 sq ft. That is the perimeter-to-area ratio at work, and it is why a small mosaic backsplash can burn through more grout than an entire large-format floor several times its size.

Anything 15 inches or larger is "large format"

Once a tile has any side of 15 inches or more, the industry treats it differently, and so should you. Three rules matter:

• The substrate has to be flat — within ⅛" over 10 ft and 1/16" over 2 ft. Big rigid tiles cannot bend over a hump, so the high spot becomes lippage and the low spot becomes a hollow that eventually cracks.
• Offset no more than ⅓, not ½. Long tiles are slightly crowned in the middle from firing. A traditional 50% brick-lay puts the neighbor's high center against your tile's low end, which maximizes lippage. A one-third offset keeps it manageable.
• Back-butter and use a big trowel. You want 80% mortar coverage in a dry room and 95% in a shower or outdoors, with no voids at the corners.

Don't forget the thinset

This calculator sizes tile and grout. The third material — thinset mortar — is priced and bought separately, and it is the one people most often run short on. Trowel notch size drives coverage, and notch size is picked from tile size:

Those are working ranges — an uneven substrate eats mortar fast, so buy one bag more than the arithmetic suggests. Our mortar calculator handles thinset, deck mud, and masonry mortar volumes if you want a firmer number.

Choosing the right grout

Grout type is chosen by joint width first, then by where the tile lives. The calculator picks for you as soon as you change the joint in Advanced options:

Picking a joint width

Joint width is partly taste and partly physics. A joint absorbs the tile's own dimensional variation, so the less consistent the tile, the wider the joint has to be. Rectified tile — mechanically ground to an exact size after firing — can go as tight as 1/16". Pressed or "calibrated" tile varies enough that ⅛" is the sensible minimum, and handmade or natural stone often needs 3/16" or more. Large-format tile should not go below ⅛" regardless of how precise it is, because you need somewhere for lippage to hide. Tighter joints also mean more visible mistakes: at 1/16", a millimetre of drift across ten tiles is obvious.

Waste factor by layout

Every edge that doesn't land on a full tile gets cut, and offcuts are usually too small to reuse. How much you lose depends almost entirely on the pattern:

Switching the layout toggle above to Diagonal / pattern moves the waste factor to 15% for you; type over it in Advanced options if your room is unusually simple or unusually chopped up.

Tile is sold by the box, not by the tile

This is the step that trips up almost every first-time order. Boxes typically hold 10–25 sq ft, and stores will not split them. Take the tile count from the calculator, divide by the tiles per box printed on the label, and round up — which usually means you end up with a bit more than the 10% waste factor implied. That is fine and, frankly, desirable.

Two more box-level rules. First, buy it all in one trip: tile is made in dye lots and batches, and two boxes of the same SKU bought a month apart can be visibly different shades. Check that the lot number matches across every box before you leave. Second, keep a full box after the job. Attic-stored spares are the only realistic way to repair a cracked tile in five years, because the line will have been discontinued.

Worked example: a 10 × 12-ft bathroom in 12×24 tile

120 sq ft plus 10% waste is 132 sq ft. Each 12×24 tile covers 2 sq ft, so that is 66 tiles — five or six boxes depending on the box count. Grout at a ⅛" joint works out to about 1.1 lb, so the smallest bag on the shelf (usually 8–10 lb) is plenty. Mortar at a ½"×½" notch covers roughly 45 sq ft per bag, so budget three 50 lb bags. Lay it in a one-third offset, not a half-brick, and check the floor with a 10-ft straightedge before you open a single box.

Worked example: a 30 sq ft subway backsplash

30 sq ft plus 10% is 33 sq ft. A 3×6 subway tile covers 0.125 sq ft, so 264 tiles — subway is usually boxed by the piece count, so expect several boxes. With a 1/16" joint the calculator switches its recommendation to unsanded grout, and you need only about 0.5 lb. Mortar at a ¼"×¼" notch stretches to nearly 90 sq ft per bag, so a single bag covers the job twice over. The real cost here is time: 264 tiles is roughly 528 joints to sponge.

What's under the tile matters more than the tile

Tile does not flex. A floor that deflects will crack the grout first and the tile second, no matter how good the installation is. The standard is L/360 for ceramic and porcelain and L/720 for natural stone — meaning a 12-ft joist span should deflect no more than 0.4" under load for tile, and half that for stone. If the floor bounces when you walk it, fix the framing before you buy tile.

Above the framing, tile needs a stable, non-shrinking substrate: cement backer board, an uncoupling membrane, or a properly cured mortar bed. Tile set directly on plywood or on drywall in a wet area is the most common failure we hear about. In showers, the waterproofing layer is a separate product from the backer board, and it is not optional.

What tile costs

As a 2026 US planning range, budget $1–$3 per sq ft for basic ceramic, $3–$8 for decent porcelain, $8–$20 for large-format or wood-look porcelain, and $10–$40 for natural stone. Thinset runs $15–$30 a bag, grout $15–$25, and backer board about $12–$15 a sheet. Professional installation typically adds $5–$15 per sq ft, more for diagonal or herringbone layouts because of the cut labor. Enter your per-tile price in Advanced options and the calculator will total the tile itself; the tile cost guide breaks down a full installed budget. Weighing tile against a floating floor? See tile vs LVP.

Frequently asked questions