Tile Calculator

How to Use This Calculator

A tile calculator tells you exactly how many tiles and boxes to buy for any floor or wall, based on room dimensions, tile size, and a waste allowance for cuts at edges. Measure room length and width in feet. Choose a tile size from the quick-pick buttons or enter custom dimensions in inches. Select a waste percentage: 10% covers cuts at walls for a straight grid layout, 15% for diagonal patterns or irregular rooms, 20% for premium tile where you want to pick the best pieces. Enter tiles per box if your tile comes in boxes — this unlocks the box count. Add a price per box for a total cost estimate. The result shows individual tile count first, then box count, then cost.

How to Calculate Tile

The formula converts everything to square feet. Multiply room length × width to get total area. Multiply by the waste factor. Divide by the area of one tile in square feet. Round up — you always buy whole tiles.

Formula: tiles = ⌈(length × width × (1 + waste% ÷ 100)) ÷ (tile width × tile length ÷ 144)⌉

The ÷ 144 converts square inches to square feet (12 × 12 = 144 sq in per sq ft).

Worked example: a 10 × 10 room with 12 × 12 tiles at 10% waste. Area = 100 sq ft. With waste: 110 sq ft. One 12 × 12 tile = 144 ÷ 144 = 1.00 sq ft. Tiles = 110 ÷ 1.00 = 110 tiles exactly.

Another example: 15 × 20 room, 18 × 18 tile, 10% waste. Area = 300 sq ft. With waste: 330 sq ft. One 18 × 18 tile = 324 ÷ 144 = 2.25 sq ft. Tiles = 330 ÷ 2.25 = 146.67 — round up to 147 tiles.

To find box count: divide tiles needed by tiles per box and round up. At 10 tiles per box: 147 ÷ 10 = 14.7, rounds to 15 boxes.

Tile Tips

Start laying tile from the center of the room, not from a wall. Find the center point of the room, snap chalk lines both ways, and start your first tile at that intersection. Working from the center ensures cut tiles at opposite walls are equal width, which looks intentional. Starting from a wall means you finish with one full row on one side and an irregular narrow sliver on the other.

Grout joint width affects how many tiles fit in a space. A 3/16-inch joint on 12 × 12 tile removes about 1.5% of the coverage area — not enough to change your tile count significantly. A 1/2-inch joint on 4 × 4 tile removes close to 11% of the coverage. For small tiles with large grout joints, add a few extra tiles to your order.

Dry-lay before you set. Arrange tiles on the floor without adhesive first to check the layout and adjust the starting point. This takes an extra 20 minutes and saves hours of grinding mistakes. It also lets you see where cuts fall and choose the most visually balanced placement.

Use the same batch number for all tiles in a room. Tile color varies between firing batches even within the same product line. Check that every box in your order shares the same batch or lot number printed on the side of the box. Mix batches and the color shift will be visible from across the room.

What to Buy

Porcelain vs. ceramic: porcelain is denser, lower water absorption, more durable, and harder to cut. Use porcelain for high-traffic floors, wet areas, and exterior applications. Ceramic is easier to cut, lighter, and less expensive — fine for walls, low-traffic areas, and above-grade interior floors.

For floors: minimum PEI rating of 3 for light residential traffic, PEI 4 for kitchens and high-traffic areas. PEI 5 for commercial. Check the box — this rating is required to be printed.

For wet areas (shower walls, shower floors, pool surrounds): look for a water absorption rating under 0.5% (vitrified or porcelain). Subway tile is glazed ceramic — it handles wet walls fine but should not be used on shower floors where grip matters.

Adhesive: use large-format tile mortar (also called medium-bed mortar) for tiles 15 × 15 and larger. Standard thinset is fine for smaller tiles. Follow manufacturer mixing ratios. Improper mixing is the leading cause of tile lippage and loose tiles discovered months after installation.

Frequently Asked Questions