Tile calculator
Tile is sold by the box and priced by the square foot, and the amount of grout depends as much on the joint width as on the area. Enter the space, tile size, and grout line, and the calculator counts tiles, boxes, thinset bags, and grout, with the right waste factor for the layout.
How the tile calculator works
Each tile covers its own footprint plus half a grout joint on every side, so the calculator adds the joint width to both tile dimensions before dividing it into the area. Waste covers the cuts along walls and around fixtures: 10 percent for a straight lay in a simple room, more for diagonal or offset patterns and for small spaces where the cuts are a larger share of the total.
Thinset coverage depends on the trowel, which depends on tile size: about 90 sq ft per 50 lb bag with a 1/4 in notch for small tile, 65 with a 1/4 × 3/8 notch for mid-size, and 40 with a 1/2 in notch plus back-buttering for large format. Grout is computed from the actual joint volume, using tile dimensions, joint width, and a 3/8 in depth, then rounded up with a 15 percent margin.
Formula
tiles = area × (1 + waste) ÷ ((tile width + joint) × (tile length + joint) ÷ 144)
grout lb ≈ area × 144 ÷ (W × L) × (W + L) × joint × 3/8 × 0.142
Example: a 10 × 8 ft bathroom floor in 12 × 24 in tile with 1/8 in joints and 10 percent waste needs 88 sq ft, which is 44 tiles or 6 boxes at 15.5 sq ft. Setting it takes 3 bags of thinset, because large-format tile needs a deep trowel, and about 11 lb of grout.
Tile layout and buying tips
- Order everything at once from one dye lot. Reorders rarely match.
- Offset plank and 12 × 24 tile no more than one third, not half. A 50 percent offset on long tile causes lippage from the natural bow in the tile.
- Use unsanded grout for joints under 1/8 in and on polished stone; sanded for anything wider.
- Rectified tile allows 1/16 in joints and a near-seamless look; pressed-edge tile needs 1/8 in or more to hide size variation.
- Measure a backsplash as length × height in feet, subtracting outlets only if there are many.
Tiling over a new slab? Let the concrete cure 28 days. For other floor coverings, see the flooring calculator.
Common sizes, already worked out
Common questions
How many 12x12 tiles do I need for 100 square feet?
About 110 tiles with 10 percent waste, since each 12 × 12 tile covers just under one square foot once the grout joint is included. In boxes of 15 sq ft, that is 8 boxes.
How much grout do I need for 100 square feet of tile?
It depends on tile size and joint width. 12 × 24 tile with 1/8 in joints needs about 12 to 14 lb. 3 × 6 subway tile with 1/16 in joints needs about 25 lb because there is far more joint per square foot. A 10 lb box covers small jobs; buy 25 lb for a floor.
How much thinset do I need?
One 50 lb bag covers roughly 90 sq ft of small tile, 65 sq ft of 12 in tile, or 40 sq ft of large-format tile that must be back-buttered. Add 10 percent and never let a bag run out mid-row.
How much extra tile should I buy?
10 percent for a straight pattern in a rectangular room, 15 percent for diagonal or brick layouts, and 20 percent for herringbone or a shower with niches and many cuts. Keep the leftovers for repairs.