🔲 Tile Calculator

How to Calculate Tiles Needed

Getting the right number of tiles prevents extra trips to the store and ensures you have matching tiles from the same dye lot.

The Basic Formula

Step by Step

• Calculate area: Length × Width in square feet
• Calculate tile coverage: Tile length × width in square feet
• Divide: Area ÷ Tile coverage = exact tiles needed
• Add waste: Multiply by waste factor and round up

Why Add Waste?

Tiles break, cuts don't always go right, and you'll want extras for future repairs. Standard practice is 10% for regular layouts, 15% for diagonal patterns.

Common Tile Sizes

Floor Tiles

• 12" × 12" – Classic, works in any room
• 18" × 18" – Modern, fewer grout lines
• 24" × 24" – Large format, makes rooms look bigger
• 6" × 24" or 8" × 48" – Wood-look plank tiles

Wall Tiles

• 3" × 6" – Subway tile, timeless
• 4" × 12" – Large subway format
• Mosaic sheets – Backsplash and accents — try our Backsplash Calculator
• Shower tile – Walls, niches, and floors — try our Shower Tile Calculator

Tiles per Square Foot

Useful for sanity-checking a box count before you leave the store:

How Much Thinset, Grout, and Backer Board?

Tile is only part of the order. These are the materials people forget until they're already at the store:

Trowel size drives thinset consumption more than anything else. A 1/4 × 1/4 in square-notch trowel covers roughly 95 sq ft per 50 lb bag; a 1/2 × 1/2 in trowel for large-format tile covers closer to 60. Match the notch to the tile: bigger tile needs a bigger notch to achieve full coverage underneath.

For large-format tile — anything with a side over 15 inches — use a medium-bed or large-format mortar rather than standard thinset. Regular thinset shrinks as it cures, which leaves hollow spots under a big tile.

Sanded or Unsanded Grout?

• Sanded grout for joints 1/8 inch and wider. The sand keeps it from shrinking and cracking.
• Unsanded grout for joints under 1/8 inch, and for polished stone or glass where sand would scratch the surface.
• Epoxy grout for heavy-stain areas. It's waterproof and needs no sealing, but it sets fast and is far less forgiving to work with.

Planning the Layout

Where you start the first tile determines how the whole floor looks. A few minutes of dry layout prevents the classic mistake of a sliver of tile along the most visible wall.

1. Find the center of the room by snapping chalk lines between the midpoints of opposing walls. Check they're square with each other.
2. Dry-lay a row in each direction from center to wall, including grout gaps, and see what the cut at the end looks like.
3. Shift the layout by half a tile if you end up with a cut narrower than about a third of a tile. Moving the start point turns two ugly slivers into two decent cuts.
4. Prioritize the sight line. Full tiles should land where you look first — the doorway, the front of a vanity — and cuts should go under cabinets and along the least visible wall.
5. Check the floor is flat. Large-format tile needs flatness within 1/8 inch over 10 feet. Fix low spots with a self-leveling underlayment before tiling, not with extra thinset.
6. Stagger plank tile by a third, not a half. Half-offsets on long planks can produce a visible lippage ridge, because most planks have slight crown along their length.

Need to work out the area first? Start with the square footage calculator, or head to the backsplash and shower tile calculators for those specific jobs.

Frequently Asked Questions

How many tiles in a box?

It varies by manufacturer. Check the box label for sq ft per box, then divide your total area by that number.

Do I count the grout lines?

For most projects, the grout gap is small enough that you don't need to account for it. Our calculator includes a gap option for precision.

What if my room isn't a rectangle?

Break the room into rectangles, calculate each separately, and add them together. Then add your waste factor.

Should I buy extra tiles?

Always. Keep 2-3 extra tiles stored away for future repairs. Tile colors can vary between production runs.

How many 12x12 tiles do I need for 100 square feet?

A 12 × 12 in tile is exactly 1 square foot, so 100 tiles covers 100 sq ft — 110 with the standard 10% waste. For 12 × 24 in tile it's 50 tiles (55 with waste), and for 18 × 18 in it's 45 (50 with waste).

How much thinset do I need?

A 50 lb bag covers roughly 60–95 square feet, depending almost entirely on trowel size. A 1/4 × 1/4 in notch gets you about 95 sq ft; a 1/2 × 1/2 in notch for large-format tile drops that to around 60.

How much grout do I need?

A 25 lb bag covers about 60–120 square feet. Small tiles and wide joints use much more than large tiles with tight joints — a mosaic backsplash can burn through grout three times faster than a 24-inch floor tile.

What size trowel should I use?

Match the notch to the tile: 1/4 × 1/4 in for tile up to about 8 inches, 1/4 × 3/8 in for 12-inch tile, and 1/2 × 1/2 in for large format. Too small a notch leaves voids under the tile, which is what causes cracking and hollow spots later.

Sanded or unsanded grout?

Sanded for joints 1/8 inch and wider — the sand prevents shrinkage cracking. Unsanded for narrower joints and for polished stone or glass tile, where sand would scratch the surface.

Do I need backer board under tile?

In wet areas, yes — cement backer board or an equivalent waterproof substrate. On dry floors over plywood, backer board or an uncoupling membrane is strongly recommended: tile set straight onto plywood cracks as the wood moves with humidity.

Where should I start laying tile?

From the center of the room, not a wall. Snap chalk lines between the midpoints of opposite walls, dry-lay a row each way, and shift the layout half a tile if you'd otherwise end with a sliver at the edge. Full tiles belong where the eye lands first.

How flat does the floor need to be for large tile?

Within about 1/8 inch over 10 feet for tile 15 inches or larger. Large-format tile can't flex to follow a dip, so a low spot becomes lippage or a cracked tile. Fix it with self-leveling underlayment before you tile — not with extra mortar.