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Tile Calculator

Find how many tiles and boxes to buy for a floor or wall, from the tile size, the grout gap and a little extra for waste.

Level: Grades 4–6

  • Common Core standard 4.MD.A.3Apply the area and perimeter formulas for rectangles in real world and mathematical problems.
  • Common Core standard 6.RP.A.3.cFind a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent.
Printable worksheet

Tile Calculator

Inputs
Units
Surface size

Typical gaps are 1/16–1/4 in (0.0625–0.25). 1/8 in = 0.125.

Printed on the box or the product listing.

Extra for cuts and breakage. About 10% for straight lays, 15% or more for diagonal patterns.

Result

Tiles needed (with waste)

130

You need about 130 tiles, which is 13 boxes of 10.

Boxes to buy
13
Tiles in those boxes
130
Tiles to cover the area exactly
117.54
Surface area
120 ft²

See the step-by-step solution ↓

Step-by-step solution

  1. Find the surface area: multiply the length by the width

    12×10=120 ft²

  2. Find the space each tile really takes: add the grout gap to its length and to its width, then multiply

    (12+0.125)×(12+0.125)=147.015625 in²

  3. Change that to ft², the same unit as your surface (144 in² per ft²)

    147.015625144=1.02094184 ft²

  4. Divide the surface area by the space one tile takes to see how many tiles cover it

    1201.02094184=117.5385

  5. Add 10% for cuts and breakage, then round up to whole tiles

    117.5385×1+0.1=129.2924=rounded up:130

  6. Divide by the 10 tiles in each box and round up, since stores sell whole boxes

    13010=13=rounded up:13

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Find out how many tiles and boxes to buy for your floor or wall. Each tile on a finished floor takes up a little more space than the tile itself. That's because of the grout line (the filled gap) around it. So the calculator divides your surface area by the space one tile and its share of grout take up. Then it adds extra for the tiles you'll cut or break.

You can describe your floor or wall by its length and width, or by an area you already know. It works in feet and inches, or in meters, centimeters and millimeters. It rounds up to whole tiles. Then it tells you how many boxes to buy, based on how many tiles come in each box.

Where it's used

Why this math matters outside the classroom:

  • Bathroom floors. A 6 × 8 ft floor is 48 ft², and 12 × 12 in tiles with 1/8 in grout lines need 48 tiles before waste.
  • Kitchen backsplash. A 10 ft by 18 in backsplash is 15 ft², or 120 subway tiles of 3 × 6 in before grout and waste.
  • Box counts. Tile is sold by the box, so 52 tiles in boxes of 10 means buying 6 boxes.
  • Grout gaps. Counting the grout joint in each tile's footprint, such as 12⅛ × 12⅛ in, slightly lowers the count for a large floor.
  • Waste allowance. Installers add 10% for cuts and breakage, so 200 tiles becomes an order of 220.

Grade level and standards: Grades 4–6; Common Core State Standards for Mathematics 4.MD.A.3, 6.RP.A.3.c. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Choose US or metric units. Then choose whether you'll enter length × width or an area you already know.
  2. Enter the tile's length and width and the grout gap you plan to use.
  3. Enter the number of tiles per box and how much extra to allow for waste.
  4. Read the number of tiles and boxes to buy. You'll also see the exact tile count before waste.

What the inputs mean

Grout gap
The width of the gap between tiles. Rectified porcelain (tiles cut to very exact sizes) is often laid with 1/16–1/8 in gaps. Handmade or rustic tiles may use 1/4 in or more. Enter 0 to leave grout out.
Tiles per box
Check the box label. It may also list the area one box covers, which you can use to double-check the result.
Waste allowance
Covers cuts at walls and around obstacles, breakage, and a few spares for future repairs. Diagonal and herringbone (zigzag) layouts need more.

Formula and method

surface area = length × width
tile footprint = (tile length + gap) × (tile width + gap)
tiles = surface area ÷ tile footprint × (1 + waste % ÷ 100), rounded up
boxes = tiles ÷ tiles per box, rounded up

A tile's footprint is the space it takes up, grout included. Each tile "owns" half the grout gap on every side, which adds one full gap to its length and to its width. The calculator then converts the footprint to square feet (÷ 144) or square meters (÷ 10,000). That puts it in the same units as your surface.

Both rounding steps go up, because you can't buy part of a tile or part of a box. Computers can leave tiny rounding errors in decimals, and the calculator ignores those. So a surface that needs exactly 110 tiles isn't rounded up to 111.

Worked example

A 12 ft × 10 ft kitchen floor will get 12 in × 12 in tiles with 1/8 in (0.125 in) grout gaps. Boxes hold 10 tiles, and you allow 10% for waste.

  1. Floor area: 12 × 10 = 120 ft².
  2. Tile footprint: (12 + 0.125) × (12 + 0.125) = 147.015625 in², which is 147.015625 ÷ 144 = 1.02094 ft².
  3. Tiles to cover the floor: 120 ÷ 1.02094 = 117.54.
  4. With 10% waste: 117.54 × 1.1 = 129.29, rounded up to 130 tiles.
  5. Boxes: 130 ÷ 10 = 13.

Result: Buy 130 tiles, which is 13 boxes of 10.

Understanding the result

The exact count shows how many tiles would cover the surface if nothing were lost to cutting. The rounded number with waste is what to buy.

If the result lands just over a full box, ask whether the store sells loose tiles. For a simple layout, you might also trim the waste allowance a little.

Assumptions and limitations

  • The surface is a rectangle or a known total area, and all of it gets tiled.
  • Tiles are rectangles laid in a regular grid, with the same gap width everywhere.
  • The waste percent is added to the exact tile count.
  • The count is based on area. It doesn't plan each cut, and narrow strips at walls can use more tiles than the area suggests.
  • Hexagon tiles, mosaic sheets and patterns that mix tile sizes need a different method.
  • Grout, tile adhesive and trim pieces aren't included.

Frequently asked questions

How much extra tile should I buy?

About 10% is common for a straight layout in a simple room. Some jobs often call for 15% or more: diagonal layouts, herringbone, small rooms with many corners, and large tiles that are hard to cut. Keeping a few spares also helps with future repairs, since tiles from different batches can vary in shade.

Does the grout gap really matter?

For large tiles it makes a small difference, but for small tiles it matters more. A 1/8 in gap on 12 in tiles changes the count by about 2%. The same gap on 4 in tiles changes it by over 6%.

How many 12 × 12 tiles are in a square foot?

Without grout, exactly one, since a 12 in square is one square foot. With a gap, each tile covers slightly more than a square foot. So you need slightly fewer than one per square foot, before waste.

Can I use this for a wall?

Yes. Enter the wall's width and height as the length and width. Or subtract windows and fixtures first, and enter what's left as a known area.

How this calculator is checked

Method: Area division with an effective tile footprint including one grout joint per dimension; ceiling rounding. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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