12x24 Tile Calculator

12x24 tile coverage chart

Offset patterns for plank tile

How many 12x24 tiles are in a box?

Box counts vary by brand and tile thickness, so read the label: it lists the tiles per box and the square feet they cover (2 sq ft per tile). Once you know it, this table gives the boxes for your floor at 12% waste, the same figures the calculator returns.

12x24 tile spacing: what each joint width changes

A wider joint uses more grout and very slightly fewer tiles, because each tile plus its share of the joint covers more floor. Grout is worked out for 3/8" thick tile with a full-depth joint, in sanded grout, using the same formula as the grout calculator.

Joint width for 12x24 is set by the tile, not by taste: rectified tile on a flat floor can go down to 1/16 in, while a calibrated tile with more size variation needs 1/8 to 3/16 in. Match the spacer or leveling clip to the joint you choose with the tile spacer guide.

Worked example: a 10 x 12 ft floor in 12x24 tile

10 × 12 ft is 120 sq ft. Add 12% for a one-third offset layout and you are covering 134.4 sq ft. Each tile is 2 sq ft, so 134.4 ÷ 2 = 67.2, rounded up to 68 tiles, which is 9 boxes of 8. With 1/8 in joints the floor takes about 6.4 lb of sanded grout, so one 25 lb bag. Six 24 in tiles are exactly 12 ft, but five 1/8 in joints add 5/8 in, so plan on trimming the last tile in each row rather than expecting full tiles wall to wall.

A “12x24” is usually not 12 by 24

Most 12x24 porcelain is made to metric 30 x 60 cm, which is 11.81 x 23.62 in. Other tiles are sold as nominal 12x24 and measure about 11 3/4 x 23 1/2 in, with the joint making up the difference. The real size is printed on the box, often as “actual size” or in millimetres. It matters for the count:

Worked example: where to start the rows in a hallway

A hallway is 88 in (7 ft 4 in) wide and the planks run along it, so their 12 in ends line up across the width. With 1/8 in joints each row step is 12.125 in. There are three ways to start, and they give very different edges:

Centring a grout joint gives two cuts of about 7.6 in, more than half a tile width and symmetrical. The other two starts leave strips you cannot set or cut cleanly. Try both centring options on paper before you snap the first line. Which one wins depends on the room width, and it takes a minute to check.

Thinset and trowel for 12x24

Use a 1/2 in square-notch trowel and a mortar labelled for large and heavy tile (LHT or medium-bed). Ordinary thinset shrinks too much in a bed that thick. Comb the ridges in straight lines parallel to the short side of the tile, back-butter every tile with a thin flat coat, then slide it across the ridges to collapse them. The standard asks for at least 80% contact in dry interior areas and 95% in showers and outdoors, with the edges and corners fully supported. Lift one tile now and then to check.

Mistakes that show up on 12x24 floors

• Not checking warpage. Put two tiles face to face. If they rock on each other, the tile has a crown. Use a one-third offset or less, or stack the joints, and use leveling clips.
• Spot-bonding. Dabs of mortar on the corners leave hollow tiles that crack under a chair leg. Full bed, back-buttered, every tile.
• Mixing boxes without checking the lot. Shade and caliber are printed on the box. Different caliber means tiles that differ in size by more than the joint can absorb. Mix boxes from one lot as you go so any shade variation is spread across the floor.
• Expecting tighter joints than the floor allows. The industry lippage allowance for joints from 1/16 to under 1/4 in is 1/32 in plus the tile's own warpage. On a floor that is not flat to 1/8 in in 10 ft, a 1/16 in joint just makes the lippage easier to see.
• Setting wall rows from the tub. On a shower wall a 12x24 weighs about 9 lb. Screw a straight ledger board one row up, set from it, and fill the bottom row last once the wall above has cured.