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How Many 12×12 Inch Tiles for a 20×20 ft Area?

A 20 by 20 foot area needs this many 12 by 12 inch tiles and boxes, including waste, grout and thinset. Here is the answer, plus a calculator you can adjust if your measurements are slightly different.

Answer: 440 tiles

How it changes with tile size

Same area, different tile size:

Tile size	12×12 in	6×6 in	12×24 in	18×18 in
Tile needed	440 tiles	1,760 tiles	220 tiles	196 tiles
Tile size	12″ × 12″	6″ × 6″	12″ × 24″	18″ × 18″

What a 20×20 ft area in 12″ × 12″ tiles actually involves

At 400 ft² this is a whole-floor job. 440 tiles is roughly 1,760 lb of material to carry in, spread and grout — plan it over more than one day, and work in sections you can finish before you walk on them. Large areas also mean the tile has to be flat and the substrate has to be right; movement in a floor this size shows up as cracked tiles at the joints.

The floor is 400 ft², or 440 ft² with your 10 percent waste allowance. Each 12″ × 12″ tile covers 1.00 ft², so you need 440 tiles — about 30 boxes at the 15 ft² per box on the label.

At 12″ × 12″ you are on the most forgiving format there is. 20 tiles across and 20 down gives you 800 linear ft of grout joint, and a 1/4 in × 3/8 in square notch trowel lays a bed deep enough to level out minor unevenness in the floor. This is the size to choose if the substrate is not perfect, because the tile is small enough to follow a slope and big enough that the grout is not a maintenance item.

Your layout: 20 tiles across, 20 down

Layout	Value	Note
Tiles across the 20 ft side	20	20 full tiles with a full tile edge
Tiles down the 20 ft side	20	20 full tiles with a full tile edge
Full grid	400 tiles	before waste, if every tile were whole
Edge tiles to cut	about 39	the perimeter run, where the cuts live
Total to buy	440 tiles	440 ft² ÷ 1.00 ft² per tile

The room is square at 20 × 20 ft, so the grid is symmetrical and a centred layout will look almost the same from any corner. A square tile in a straight lay gives you one clean grid with no pattern to line up, which is the fastest way to lay this floor.

Start from the centre, not from a wall. Walls are never square, and a layout built off one wall ends up with a widening wedge of cut tiles on the far side. Strike a centre line in both directions, dry-lay a row, then adjust the starting line so the cuts on opposite edges come out the same width.

Grout, thinset and weight

Item	Quantity	How it is worked out
Grout joint length	800 ft	2.0 ft of joint per ft² with 12″ × 12″ tiles
Sanded grout	about 8 × 25 lb bags	roughly 200 lb at a 1/8 in joint, 1/4 in deep
Thinset mortar	5 × 50 lb bags	about 95 ft² per 50 lb bag at a 1/4 in notch
Tile weight	about 1,760 lb	4 lb per ft² installed; porcelain and stone are heavier
Notch trowel	1/4 in × 3/8 in	matched to the tile size

Grout is the figure people get wrong, and it is because of joint length rather than floor area: a 12″ × 12″ tile puts 2.0 ft of joint into every square foot. Check the coverage printed on the bag you buy — the numbers above assume a 1/8 in joint, and widening to 3/16 in adds roughly half again. Buy a spare bag: a second bag from a different batch can be a shade off, and part-used bags are the only thing harder to match than discontinued tiles.

Buying the boxes

440 tiles is 30 boxes if every box really covers 15 ft². Do not trust the tile count in a box — boxes are labelled by coverage in square feet, and the tile count changes with size and with the manufacturer's packing. Read the ft² figure from the box you are actually going to buy, and if it differs from 15, rework the count from the tile size above rather than the box.

Buy the whole floor in one purchase and check the dye lot code on every box before you leave the store. Tiles are made in batches that vary slightly in shade and calibration, they get discontinued constantly, and a floor laid from two different lots shows the seam. Keep the leftovers. A cracked tile three years from now is unfixable unless you have a spare in a matching lot, and one box of spares is the cheapest insurance in the job.

Laying it

Make the substrate right first. Tile will not fix a bouncy floor or a damp wall. Backer board or a tile membrane over the subfloor, and a waterproof membrane in any wet area, before a single tile goes down.
Find the centre of the room, strike both centre lines at right angles, and dry-lay a row in each direction. Adjust the start so the edge cuts are even.
Spread adhesive in small areas — a square metre at a time — with the flat side of the trowel first and then the notched side. Adhesive that has skinned over before the tile lands will not bond.
Back-butter any tile you cut, and press with a slight twist to collapse the ridges. Aim for full coverage, not just contact at the corners.
Use 1/8 in to 3/16 in spacers and check every few courses for level. Once the adhesive sets, the only way to fix a lip is to break the tile out.
Let the adhesive cure before grouting — 24 hours is normal, longer in a cold or damp room.
Grout with a rubber float held at 45 degrees, work it in small sections, and wipe the surface before it sets on the tile face. Haze comes off with a dry cloth, set grout does not.
Seal cement-based grout once it is fully cured, and seal natural stone before it is laid. This floor has about 800 ft of joint to look after.

Common questions

How many 12×12 inch tiles do I need for a 20×20 ft area?

440 tiles. The floor is 400 ft² and each 12″ × 12″ tile covers 1.00 ft², so 440 ft² with your 10 percent waste allowance divides out at 440 tiles — about 30 boxes at 15 ft² per box.

How many boxes of tile is that?

30 boxes at 15 ft² per box. Always confirm the coverage on the label of the box you are buying rather than counting tiles — packing varies by manufacturer, and it is the square footage that matters.

How much waste should I allow for a 20×20 ft floor?

Your page is worked at 10 percent. For a straight lay in a rectangular room 10 percent is normal; go to 15 percent for a diagonal or herringbone layout, for a room full of doorways and fittings, or for large-format tiles where a single miscut is expensive. This floor needs 20 tiles across and 20 down, so roughly 39 tiles are on an edge and will be cut.

How much grout and thinset do I need?

About 8 × 25 lb bags of grout and 5 × 50 lb bags of thinset, based on 800 ft of grout joint and a 1/4 in notch trowel. 12″ × 12″ tile puts 2.0 ft of joint in every square foot, so smaller tiles and wider joints both use more grout than this estimate.

How do I lay out 12×12 inch tiles in a 20×20 ft room?

Centre the grid and work outwards. You need 20 tiles across and 20 down; the edge cuts are the none on the 20 ft side and the none on the 20 ft side. If those cuts come out as slivers, shift the centre line by half a tile to balance them.