Tile Calculator
Enter your room dimensions and tile size to instantly find out how many tiles, boxes, and bags of thin-set mortar your project requires. The calculator accounts for grout line spacing and a configurable waste factor.
What is Tile?
A tile calculator estimates the number of tiles, boxes, and setting materials needed to cover a floor or wall area. Accurate tile estimation prevents the two most common tiling headaches: running short mid-project (and discovering your tile lot is no longer available) and over-ordering expensive material that cannot be returned once opened. The calculation begins with the total floor area in square feet. The key detail that separates a good estimate from a rough guess is accounting for grout lines. Each tile effectively covers an area slightly larger than the tile itself because the grout joint adds width between tiles. For a 12-inch tile with a standard 1/8-inch grout line, the effective coverage per tile is 12.125 by 12.125 inches, or about 1.021 square feet. Over a large floor, this grout spacing means you need slightly fewer tiles than a simple area-divided-by-tile-size calculation would suggest. The waste factor is critical. Tiles must be cut to fit along walls, around obstacles, and at doorways. Straight layouts in rectangular rooms need about 10 percent waste. Diagonal layouts, L-shaped rooms, and intricate patterns like herringbone can require 15 to 20 percent waste. Large-format tiles (24 inches and above) also produce more waste because cut pieces are harder to reuse. Tiles are sold by the box, typically 10 tiles per box for standard 12-inch ceramic tiles, though counts vary by tile size and manufacturer. Always buy by the full box and keep at least one box of extra tiles for future repairs, since color lots change between production runs. Thin-set mortar is the adhesive that bonds the tile to the substrate. Coverage depends on trowel notch size: a 1/4-inch square-notch trowel covers approximately 70 square feet per 50-pound bag for standard floor tiles. Larger tiles require a larger trowel (1/2-inch), which uses more thin-set and reduces coverage to around 40-50 square feet per bag. This calculator gives you a complete materials list for standard floor tile installations so you can order everything in a single trip.
How to Calculate
- Measure the room length in feet
- Measure the room width in feet
- Enter the tile size in inches (one side of a square tile)
- Enter the grout line width in inches (1/8 inch is standard for floor tile)
- Set the waste factor (10% for rectangular rooms, 15% for diagonal or complex layouts)
- Review tiles needed, boxes to purchase, and thin-set bags
Formula
Floor Area = Room Length (ft) x Room Width (ft) Effective Tile Area = (Tile Size + Grout Width)^2 in square inches Tiles Needed = ceiling(Floor Area / (Effective Tile Area / 144) x (1 + Waste%/100)) Boxes Needed = ceiling(Tiles Needed / 10) Thin-Set Bags = ceiling(Floor Area x (1 + Waste%/100) / 70) Where 144 converts square inches to square feet, 10 is the standard tiles per box, and 70 sq ft is the average coverage per 50 lb bag of thin-set mortar using a 1/4-inch square-notch trowel.
Example Calculation
A 12 ft x 10 ft bathroom floor using 12-inch tiles with 1/8-inch grout lines and 10% waste: Floor Area = 12 x 10 = 120 sq ft Effective Tile Area = (12 + 0.125)^2 = 12.125^2 = 147.02 sq in = 1.021 sq ft Tiles (raw) = 120 / 1.021 = 117.5 tiles Tiles with 10% waste = ceiling(117.5 x 1.10) = ceiling(129.3) = 130 tiles Boxes = ceiling(130 / 10) = 13 boxes Thin-Set Bags = ceiling(120 x 1.10 / 70) = ceiling(132 / 70) = 2 bags
Frequently Asked Questions
Why do grout lines matter in the tile count?
Grout lines add spacing between tiles, which means each tile effectively covers a slightly larger area than the tile alone. For small tiles or wide grout joints, this difference adds up and can save you from over-ordering. For 12-inch tiles with 1/8-inch grout, the effect is small, but for 4-inch mosaic tiles with 1/8-inch grout, the grout accounts for about 6% of the floor area.
How many extra tiles should I keep for repairs?
Keep at least 5-10% of your total order as spares, stored flat in a dry location. Tile colors vary between production lots, so matching tiles years later can be impossible. One full box of extras is a good rule of thumb for most rooms.
What waste factor should I use for a diagonal tile layout?
Use 15% for diagonal layouts in rectangular rooms. The 45-degree angle creates more cut pieces along every wall, and the triangular offcuts are harder to reuse than straight-cut pieces. For herringbone or chevron patterns, use 15-20%.
Can I use this calculator for wall tile?
Yes. Enter the wall height as the length and the wall width as the width. For multiple walls, calculate each wall separately and add the tile counts together. Wall tile waste is typically 10-15% since there are fewer obstacles than floors.
What size trowel notch should I use?
For tiles up to 12 inches, use a 1/4-inch square-notch trowel (about 70 sq ft per bag). For 13-16 inch tiles, use a 3/8-inch square-notch. For tiles 18 inches and larger, use a 1/2-inch square-notch trowel, which reduces thin-set coverage to about 40-50 sq ft per bag.
How much grout do I need in addition to thin-set?
Grout is separate from thin-set. A 25-pound bag of unsanded grout covers approximately 200 square feet of 12-inch tile with 1/8-inch joints. Sanded grout (for joints wider than 1/8 inch) covers approximately 100 square feet per 25-pound bag. This calculator focuses on thin-set; estimate grout separately based on your joint width.