How to use the tile calculator
- Choose floor or wall. For a floor, enter the room length and width. For a wall, backsplash or shower, enter the width and the tiled height. For a three-wall shower, add the widths of all three walls together.
- Subtract what you won’t tile — a vanity or tub footprint on a floor, a window or niche on a wall.
- Pick the tile size and grout joint. Joints matter: on small tiles, a ⅛ in joint changes the tile count noticeably.
- Choose the layout pattern. The waste allowance updates automatically (10% straight, 12% offset, 15% diagonal, 20% herringbone). You can still override it.
- Enter the coverage per box printed on the carton, and the tile thickness and trowel size for the grout and thin-set estimates.
Tile calculator formula
Tiles = area × tiles per sq ft × (1 + waste %) → round up
Boxes = tiles × tile area ÷ sq ft per box → round up
Grout (lb) ≈ area × tiles per sq ft × joint volume per tile × 0.065 lb/in³
Including the joint in the tile footprint is what makes this more accurate than “area ÷ tile size”. A 3 × 6 in subway tile with a 1/16 in joint covers 7.76 tiles per sq ft, not 8 — on an 88 sq ft shower that’s 21 tiles of difference before waste.
Thin-set coverage by trowel
| Trowel notch | Typical tile | Coverage per 50 lb bag |
|---|---|---|
| ¼ × ¼ in square | Up to about 8 in | ≈ 90–100 sq ft |
| ¼ × ⅜ in square | 8–15 in | ≈ 60–67 sq ft |
| ½ × ½ in square | Large format, 15 in and up | ≈ 42–47 sq ft |
These ranges come from CUSTOM Building Products’ published VersaBond coverage chart (linked in Sources & assumptions below); the calculator uses the low end of each range so you don’t run short. Back-buttering large tiles (recommended for anything over 15 in) uses roughly 20% more.
Worked examples
How many tiles do I need for a 10×10 room?
With 12 × 12 in tile and ⅛ in joints, 100 sq ft needs 97.9 tiles before waste. With 10% for a straight layout: 108 tiles. Using 12 × 24 in tile instead: 49.2 tiles, plus 10% = 55 tiles, which is 7 boxes at 16 sq ft per box, about 6 lb of grout and two 50 lb bags of thin-set with a ¼ × ⅜ in trowel.
Tile for shower walls
A standard alcove shower with a 5 ft back wall and two 3 ft side walls, tiled 8 ft high, is (5 + 3 + 3) × 8 = 88 sq ft. In 3 × 6 in subway tile with 1/16 in joints and a 12% offset-pattern allowance you need 765 tiles — 10 boxes at 10 sq ft per box — and, with ⅜ in thick tile, about 10 lb of grout.
Subtract niches and windows only if they’re large. Their edges need bullnose or trim pieces, which often uses up the tile you “saved”.
Pattern waste and buying tips
- Herringbone and diagonal layouts waste more because every edge piece is an angled cut. Budget 15–20%.
- Large-format tile (any side 15 in or longer) breaks more easily and has fewer reusable offcuts — lean toward the top of the waste range.
- Buy trim separately. Bullnose, pencil liners and edge profiles are sold by the piece or linear foot; measure every exposed edge.
- Check shade and caliber codes on each box and mix tiles from several boxes as you set them to blend variation.
- Keep a few spare tiles for future repairs — the same color is often discontinued within a few years.
- Grout coverage varies by product. Use the result as a guide and confirm against the chart on the bag you buy, especially for epoxy grout.
Laying plank flooring elsewhere? See the flooring calculator. Need cement board or drywall behind the tile? Try the drywall calculator.
Tiles per square foot by size
| Tile size | Joint | Tiles per sq ft |
|---|---|---|
| 3 × 6 in | 1/16 in | 7.76 |
| 4 × 4 in | 1/16 in | 8.73 |
| 6 × 24 in | ⅛ in | 0.97 |
| 12 × 12 in | ⅛ in | 0.98 |
| 12 × 24 in | ⅛ in | 0.49 |
| 24 × 24 in | ⅛ in | 0.25 |
Sources & assumptions
How this calculator gets its numbers. Full method: our methodology.
- Tile count = area ÷ tile face area, plus a pattern allowance: 10% straight, 12% offset, 15% diagonal, 20% herringbone.
- Thin-set bags use the low end of the maker's coverage range for each trowel notch, so the count errs on the side of enough mortar.
- Grout is estimated from joint volume (about 0.065 lb per cubic inch, back-calculated from the maker's coverage chart). Everything is rounded up.
Sources
- Custom Building Products, VersaBond Professional Thin-Set Mortar (coverage chart). Square-foot coverage per 50 lb bag by trowel notch.
- Custom Building Products, Polyblend Plus Sanded Grout (coverage chart). Coverage per 25 lb bag by tile size and joint width.
Last reviewed . Product figures vary by brand; the label on what you buy wins.
Frequently asked questions
How many tiles do I need for a 10x10 room?
A 10 × 10 ft room is 100 square feet. With 12 × 12 inch tiles and 1/8-inch grout joints you need about 98 tiles before waste, or 108 with a 10 percent allowance. With 12 × 24 inch tiles you need about 55 including waste.
How much extra tile should I buy?
Ten percent for a straight layout, about 12 percent for an offset or brick pattern, 15 percent for diagonal and 15 to 20 percent for herringbone. Add a little more for large-format tile or rooms with lots of corners.
How do I calculate tile for shower walls?
Add the widths of all tiled walls and multiply by the tiled height. A 5 ft back wall and two 3 ft side walls tiled to 8 ft is 88 square feet. Enter that as a wall in the calculator and subtract any large window.
Do grout lines change how many tiles I need?
Yes, slightly. Each tile plus its joint covers more area than the tile alone, so you need a few percent fewer tiles. The effect is biggest with small tiles: 3 × 6 inch subway tile with 1/16-inch joints is about 7.76 per square foot instead of 8.
How much thin-set do I need?
A 50 lb bag covers roughly 90 to 100 square feet with a 1/4 × 1/4 inch notch trowel, 60 to 67 with 1/4 × 3/8, and 42 to 47 with 1/2 × 1/2. Larger tiles need bigger notches and more mortar.
How much grout do I need?
It depends on tile size, joint width and tile thickness. For 12 × 12 inch tile 3/8 inch thick with 1/8-inch joints, plan on about 0.07 lb per square foot, so a 25 lb bag covers roughly 350 square feet. Small mosaics with wide joints use many times more.