Tile Grout Calculator
Enter your tile size, joint width, joint depth (≈ tile thickness), and area to get pounds of grout and the number of bags to buy. Uses the TCNA/Laticrete volume formula.
Tile & Area
Grout Joint
Grout Type & Bag Size
How the grout formula works
Step 1 — joint length per unit area (TCNA/Laticrete geometry)
joint_len_per_area = (tile_L + tile_W) / (tile_L × tile_W) [1/in] Each tile shares half its perimeter with its neighbours, netting (L+W) of joint per tile face area L×W. A 12×12 yields 24/144 = 0.167/in; a 2×2 mosaic yields 4/4 = 1.0/in — 6× more grout for the same area.
Step 2 — grout weight per square foot
lb/sq ft = joint_len_per_area × joint_width × joint_depth × density (lb/in³) × 144 Density: sanded 104 lb/ft³ (= 0.0602 lb/in³), unsanded 90 (= 0.0521), epoxy 110 (= 0.0637). Multiplying by 144 in²/ft² converts the per-in² result to per-ft².
Step 3 — total pounds and bags
grout_lb = lb/sq ft × area × (1 + waste%/100) bags = ⌈ grout_lb / bag_size − 1e−9 ⌉ The −1e−9 float guard prevents a spurious extra bag when the result lands on exactly a whole number due to floating-point rounding.
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Frequently Asked Questions
Total tiled area (sq ft), tile length and width (in), grout joint width (in), joint depth — which equals your tile thickness (in), grout type (sanded / unsanded / epoxy), bag size (lb), and waste allowance (%). Every variable that controls grout consumption is an explicit input.
Use sanded grout for joints 1/8 in (3 mm) or wider — the sand aggregate resists shrinkage in wider joints. Use unsanded for joints narrower than 1/8 in, glass tile, or polished marble where sand would scratch the surface. Choose epoxy when you need chemical resistance (kitchen counters, food-service areas) — it is denser at 110 lb/ft³ vs 104 for sanded and 90 for unsanded.
Joint volume is width × depth × length. Double the depth and you double the grout needed. The default 5/16 in depth matches typical ceramic and porcelain tile thickness; mosaic sheets on mesh may have joints only 1/4 in deep while thick paver or quarry tile can be 3/4 in or more. Enter your actual tile thickness for an accurate result.
With a 1/4 in joint, 5/16 in depth, sanded grout, and 10% waste: the coverage rate is 0.113 lb/sq ft. Raw grout ≈ 11.3 lb; with waste ≈ 12.4 lb. One 25 lb bag is sufficient. At a 1/8 in joint the same tile needs only about 0.056 lb/sq ft — still one bag for 100 sq ft.
The comparison chart shows the grout coverage rate (lb per sq ft) for five common tile sizes — 2×2 mosaic, 3×6 subway, 12×12, 12×24, and 24×24 — at your chosen joint width and depth. It makes the 6× difference between mosaic and large-format tile immediately visible.