Tile Calculator

Enter the area, the tile size, the grout joint and an allowance to estimate the number of tiles and boxes.

Area to cover

Enter the area directly. Adding several surfaces or subtracting doors and windows is not done for you.

Unit for the tile and joint sizes

Tile width

Tile length

Grout joint width (0 is allowed)

The joint width is added to both the width and the length of a tile to get the area one tile takes up. Enter fractions as decimals (1/8 in is 0.125, 3/16 in is 0.1875).

Allowance for waste (%, added on top of the net number of tiles)

An allowance of 10% means 1.1 times the net number. Use it for breakage, cuts at the edges and spares. No typical figure is suggested.

Tiles per box (optional)

Enter the number of tiles in one box to see the number of boxes (rounded up). Boxes sold by area (square feet per box) are not calculated by this tool.

Tiles needed (rounded up) —

Details
Area one tile takes up (tile + grout joint)	—
Net number of tiles (without the allowance)	—
Tiles with the allowance (before rounding up)	—
Boxes needed (rounded up)	—

This is an estimate: the area divided by the area one tile takes up (including the joint). A real layout, with cuts at the edges, pattern and installation method, can need a different number. Use the allowance for tiles lost to cuts. Check the product's size (actual or nominal) in the manufacturer's information.

The number copied is the number of tiles (a whole number).

How it is calculated

Area one tile takes up = (width + joint) × (length + joint).
Net number of tiles = area ÷ the area one tile takes up.
Tiles with the allowance = net number × (1 + allowance).
Tiles needed = that number rounded up, once, at the end. The net number is not rounded up first, because rounding twice can give a larger number.
Boxes = tiles needed ÷ tiles per box, rounded up (only when you enter tiles per box).

The calculation uses exact fractions. Conversions use 1 in = 25.4 mm = 0.0254 m, 1 ft = 0.3048 m and 1 ft² = 0.09290304 m² (the inch and foot definitions, NIST SP 811).

Tiles needed and boxes needed are different

Tiles needed is a count of single tiles.
Boxes needed comes from the number of tiles in a box. If your tiles are sold by the square foot per box, divide the tiles you need by the tiles in a box, or enter the count of tiles per box from the packaging.
Buying a bit more than the estimate helps with future repairs, because tiles from different production lots can differ in color.

Example

100 ft² to cover, 12 in × 12 in tiles, a 1/8 in (0.125 in) joint, a 10% allowance and 10 tiles per box:

One tile takes up (12 + 0.125)² = 147.015625 in² = about 1.0209 ft²
Net number: 100 ÷ 1.0209 = about 97.95 tiles
With the allowance: about 107.74 → 108 tiles
108 ÷ 10 = 10.8 → 11 boxes

What is not included

The layout is not planned. Edge cuts, patterns, diagonal layouts and the position of the first row are covered only by the allowance.
A perimeter joint, uneven walls and the thickness of the adhesive are not included.
The tile size must be the real size you will lay, including whether it is the nominal or actual size.

Sources

The inch and foot definitions come from NIST SP 811 Appendix B.8 (rows read word for word), checked on November 1, 2026. The tile formula is a general calculation, not taken from a source.

NIST SP 811, Appendix B.8

Frequently asked questions

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

With no joint and no allowance, 100 tiles. With a 10% allowance, 110. A joint changes the area one tile takes up, so the number is a little lower.

How do I enter a joint of 1/8 inch?

Enter 0.125 and choose inches.

Does the tool work out boxes?

Yes, if you enter the number of tiles per box. It does not handle boxes sold by area.