Tile Calculator

How this calculator works

The calculator counts tiles from geometry rather than a generic square-foot rule: each tile plus its share of the grout joints covers slightly more than the tile itself, so tile size and joint width both change the count. The core formulas are:

tiles per sq ft = 144 ÷ ((tile length + joint) × (tile width + joint))
area            = sum of (length × width − subtracted) per area   (never below 0)
tile count      = area × tiles per sq ft                          → rounded up
buy tiles       = tile count × (1 + waste %)                      → rounded up
boxes           = buy tiles ÷ tiles per box                       → rounded up

Setting materials are figured on the measured area, not the purchase amount — the waste tiles in your garage never get mortared down. Thinset defaults to about 60 sq ft per 50 lb bag (a 1/4-in square-notch trowel), grout to about 100 sq ft per 10 lb bag at 12 × 12 tile with 1/8-in joints. Both are clearly labeled assumptions you can edit, because real coverage swings widely with trowel size, tile size, and joint depth.

If you enable backer board, sheets are counted at 15 sq ft per 3 × 5 ft sheet across all areas entered. A labor rate, when you provide one, multiplies the net tiled square footage — not the padded purchase quantity.

Worked example: bathroom floor plus tub surround

Say you're tiling a 10 × 8 ft bathroom floor (80 sq ft) and a 7 ft long × 5 ft high tub-surround wall (35 sq ft) with 12 × 12 in tile, 1/8-in joints, and 10% waste:

• Area: 80 + 35 = 115 sq ft.
• Tiles per sq ft: 144 ÷ (12.125 × 12.125) = 0.979 — slightly under 1, because each grout joint covers a little area for free.
• Tile count: 115 × 0.979 = 112.6 → 113 tiles; with 10% waste, 124.3 → buy 125 tiles.
• Boxes: at 10 tiles per box, 125 ÷ 10 = 12.5 → 13 boxes.
• Thinset: 115 ÷ 60 = 1.9 → 2 bags (50 lb).
• Grout: 115 ÷ 100 = 1.15 → 2 bags (10 lb).

Enter those two areas above and you'll see exactly these numbers. Change the joint to 1/4 in or the tile to 24 × 12 and watch the count shift — that's the geometry doing its job.

How to measure for tile

• Floors: measure wall to wall at the longest and widest points, in feet. Split L-shapes into rectangles and enter each as its own area row.
• Walls:enter the wall's length and the height you'll tile to — full height for a shower, maybe 4 ft for a wainscot. A three-wall tub surround is three rows (or one row using the combined length).
• Use the subtract field for windows, door openings, and the tub face — openings inside an area you already measured. Niches roughly cancel out (you skip the opening but tile its inside), so most people just ignore them.
• Measure edge trim separately: walk every exposed tile edge — the top of a wainscot, shower-curb edges, outside corners — and total the linear feet for the trim field.

Our guide How to Calculate Square Footage covers splitting odd shapes into rectangles.

Buying tile and setting materials

• Buy all tile from one lot. Shade (caliber/lot) codes are printed on the box; two lots of the same tile can differ in tone and even size. Order the full amount, waste included, in one purchase.
• Match the mortar to the tile and setting.Large-format tile (any side 15 in or longer) needs a medium-bed/LFT mortar; wet areas and some porcelains call for specific mortar classes. The bag states what it's rated for.
• Pick grout by joint width. Traditionally sanded grout for joints 1/8 in and wider, unsanded for narrower — though modern high-performance grouts often span both. Buy enough of one batch to finish; color can shift between batches.
• Buy where returns are easy. Because thinset and grout coverage vary so much in practice, the cheap insurance is an extra bag of each from a store that takes back unopened bags.

Common estimating mistakes

• Assuming one 12 × 12 tile per square foot.With grout joints, it's about 0.98 tiles per square foot — close, but on a big floor the difference is real, and for other sizes the "one per foot" shortcut falls apart entirely.
• Under-buying waste. Every perimeter cut, every out-of-square wall, and every cracked tile comes out of your stack. 10% suits grid and offset layouts; diagonal needs about 15% and herringbone 18%, because angled cuts are rarely reusable.
• Trusting default thinset coverage on large tile. Bigger tile means a bigger trowel and often back-buttering — coverage per bag can drop by half compared to the 1/4-in-trowel default here.
• Forgetting trim and the substrate. Bullnose or metal edge profiles are priced per foot and add up fast, and a floor that needs backer board also needs backer screws and mesh tape.

Limitations

This tool estimates rectangular areas and treats mosaic sheets, planks, and specialty patterns as ordinary tiles of their stated size — real cut waste on complex patterns can run higher than any preset. Thinset, grout, and backer counts are planning-level assumptions applied uniformly to all areas (walls and floors alike), and the calculator doesn't design waterproofing, movement joints, or substrate build-up, all of which are governed by the product instructions and industry standards for your specific installation. Treat the output as a shopping-planning list, not an installation spec.