Tile Calculator

Calculate how many tiles you need for a floor, wall or backsplash. Enter the area, tile size and grout gap to get tile count, boxes and square footage with waste.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To find how many tiles you need, convert the area to square inches and divide by the size of one tile plus its grout joint, then add 10% for cuts. An 80 sq ft floor needs 40 tiles of 12 x 24 in with a 1/8 in joint, or 44 tiles including waste.

Results

Tiles to buy: 44 tiles; 40 tiles plus 10% waste
Area to cover: 80 sq ft; Buy about 88 sq ft including waste
Tile size: 12 x 24 in; 2 sq ft per tile

Tile formula

Area (sq in) = Length (ft) x Width (ft) x 144
Tile footprint (sq in) = (Tile width + grout gap) x (Tile length + grout gap)
Tiles = Area / Tile footprint x (1 + waste %), rounded up

Worked example

A 5 x 8 ft bathroom floor with 12 x 12 in tile and a 1/8 in joint: 40 sq ft x 144 = 5,760 sq in. Each tile occupies 12.125 x 12.125 = 147 sq in. 5,760 / 147 = 39.2 tiles, plus 10% waste = 43.1, so buy 44 tiles.

Quick reference

Tiles per 100 sq ft with a 1/8 in grout joint (before waste)
Tile size	Tiles per sq ft	Tiles per 100 sq ft
3 x 6 in (subway)	7.5	752
4 x 4 in	8.5	846
6 x 6 in	3.8	384
12 x 12 in	0.98	98
12 x 24 in	0.49	49
18 x 18 in	0.44	44
24 x 24 in	0.25	25

How to calculate tile

Convert the area to square inches, then divide by the footprint of one tile plus its grout joint. A 12 by 24 inch tile with a 1/8 inch joint occupies 12.125 by 24.125 inches, or 292.5 square inches. An 80 square foot floor (11,520 square inches) needs about 40 tiles before waste.

Add 10 percent for straight layouts and 15 percent for diagonal, herringbone or rooms with many cuts. Large-format and natural stone tiles also chip more easily, so lean toward the higher figure.

Grout gap and layout

A larger grout gap slightly reduces the tile count but is mostly a design choice. Rectified porcelain is often set at 1/16 inch; standard ceramic at 1/8 to 3/16; handmade or natural stone at 1/4 inch. Enter the gap you plan to use for an accurate count.

Key facts

A 12 x 12 in tile covers 1 sq ft, a 12 x 24 in tile covers 2 sq ft, and an 18 x 18 in tile covers 2.25 sq ft.
Add 10% waste for straight layouts and 15% for diagonal or herringbone patterns.
Typical grout joints: 1/16 in for rectified porcelain, 1/8 to 3/16 in for ceramic, 1/4 in for natural stone.
Subway tile at 3 x 6 in takes about 8 tiles per square foot before waste.

Frequently asked questions

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

About 100 tiles before waste (one 12x12 tile is one square foot), so buy 110 to 115 tiles to allow for cuts and breakage.

How much extra tile should I buy?

10% for a simple straight layout, 15% for diagonal or patterned layouts. Keep leftovers for future repairs since dye lots change.

Does the grout gap change how many tiles I need?

Slightly. A wider joint means each tile covers a little more area, so you need marginally fewer tiles. For most jobs the difference is under 3%.

Sources and references

Grout FAQ: standards for grout joint size and variation (Tile Council of North America)
2025 TCNA Handbook for Ceramic, Glass, and Stone Tile Installation (Tile Council of North America)
TB89 Grout Coverage Rates: Understanding Variations (technical bulletin) (Custom Building Products)

Next steps for this project

The usual order for a flooring & tile project. See all flooring & tile calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.