Tile Grout Coverage Calculator — sq ft tiles, thinset, cost
How to use this calculator
Pick the room shape, enter feet and inches, then choose tile size and grout joint — the count reflects nominal tile + joint (a 12×12" tile on a ⅛" line actually covers 12.125×12.125"). Pattern auto-sets waste: 0% straight grid, +10% running bond, +15% diagonal/herringbone. The bag and sheet outputs drive a real materials list you can hand to the supplier without re-doing math on the desk.
Cost — price per tile or per box, thinset per bag, grout per bag, backer board per sheet; the grand total sums only the optional sections you enable.
Thinset — a 50 lb bag covers ~80 ft² with a ¼"×¼" notch, ~60 ft² with ¼"×⅜", and ~50 ft² with ½"×½" (ANSI A108).
Grout — sand grout volume is computed from joint width × tile thickness × joint length, then divided by ~230 in³ per 25 lb bag.
Backer board — ½" cement board, 3×5 ft sheets (15 ft²), 10% added for cuts.
Saved Calculations
| Time | Shape | Area ft² | Tile | Tiles | Thinset | Grout | Backer | Total |
|---|
Grout calculator for square feet
Net tiles = floor area ÷ (tile width + joint)(tile height + joint), rounded up; the joint is added so a 12×12" tile on a ⅛" grout line actually covers 12.125×12.125". Pattern waste is then applied: a straight grid loses almost nothing, a running-bond offset wastes ~10%, and 45° diagonal or herringbone wastes ~15% from edge cuts. Always order full boxes and keep one spare box for future repairs.
Thinset mortar coverage
Coverage tracks trowel notch: a ¼"×¼" square-notch trowel spreads a 50 lb bag over ~80 ft², ¼"×⅜" over ~60 ft², and ½"×½" (large-format / uneven substrate) over ~50 ft², in line with ANSI A108/A118 and trowel-manufacturer charts. Back-buttering large tiles uses more. For wall layout, pair this with the drywall sheet & tape calculator when the substrate is gypsum board.
Grout coverage formula
For a grout calculator square feet estimate, grout volume = (tile perimeter × joint width × tile thickness) ÷ 2 per tile (joints are shared between adjacent tiles), summed over the tile count and divided by ~230 in³ per 25 lb bag of sanded grout — roughly 90 ft² for 12×12" tile on a ⅛" joint. Smaller tiles, wider joints, and thicker porcelain all raise grout use.
On install day
Three estimator misses we see all the time. Round to full boxes — a 100 ft² floor at 12×12" is roughly 110 tiles with 10% waste, but a typical box holds 10–15 tiles, so you almost always pay for one extra box; keep that spare for repairs. Backer board, not drywall — wet areas need ½" cement board (3×5 ft sheets, 15 ft² each) per ANSI A108.11 and IRC §R702.4.2; the calculator adds 10% for cuts and seams. Thinset/grout pricing in 2025 — 50 lb modified thinset runs $18–28/bag, 25 lb sanded grout $15–22/bag, basic ceramic tile $1.50–4/ft² and porcelain $3–10/ft²; large-format tiles need ½"×½" notch trowels and back-buttering, which raises bag count 20–30%. Comparing floor finishes? See the flooring box calculator or the carpet calculator, and the paint calculator for the walls. Tiling onto a masonry wall? Cross-check with the brick wall calculator.
