Wall, Floor & Shower Grout Calculator — Surface-Specific Settings

Nothing in the math and everything in the presets. A wall grout calculator runs the same joint-volume formula, but it assumes narrow joints (1/16 in), unsanded grout (because sanded grains will not fit a 1/16 in gap), shallow tile (1/4 in) and a slim 5% waste margin. A floor grout calculator opens the joint to 1/8 or 1/4 in, switches to sanded grout for abrasion resistance, uses the full tile thickness as depth and carries a 10% margin because foot traffic means more reworking during clean-up. The formula is identical; the defaults are not.

For coverage math, almost not at all — both sit in the 1.6–1.7 kg/L density band and use the same joint geometry. What changes is edge finish. Porcelain tiles are rectified (precise edges that allow 1/16 in joints); many ceramic floor tiles are cushion-edged (the factory bevel means the joint you see is wider than the gap you cut). A ceramic tile grout calculator must assume the visible joint width, which often runs 1/4 in or more. A rectified porcelain floor at 1/8 in joints uses about half the grout of a cushioned ceramic floor at 1/4 in.

Shower grouting loses material to water — every sponge rinse carries a little grout off the wall, and wet-area clean-up requires more passes than a dry floor. The 15% margin is the industry rule-of-thumb that covers sponge dilution, the slurry that washes into the pan, and the small re-touch batches you mix after the main pass. It also covers the one surface a flat calculator misses: you measure shower walls, floor and curb separately, and each has its own tile size and joint depth. The shower preset uses a representative 6 × 6 in wall tile, but real shower work often has three geometries in one enclosure.

Only in the defaults. A ceramic tile grout calculator search usually wants two things the generic calculator leaves to the user: unsanded vs sanded (narrow ceramic joints need unsanded; wide floor joints need sanded), and a density assumption (ceramic grouts cluster around 1.6 kg/L, while epoxy runs 1.7 kg/L). Once those are set, the calculation is the same volume-to-weight chain. The main grout calculator on this site lets you override density; the surface presets on this page pre-fill the overrides for you.

Treat it as its own surface, not part of the wall calculation. A 2 × 2 in mosaic at 1/8 in joints and 1/4 in depth holds 0.73 L/m² of joint — about 3.7× the volume of a 12 × 12 in floor at the same joint width. For a 30 ft² shower pan that is roughly 2.0 L of joint, which at 1.7 kg/L is 3.4 kg of powder before the 15% wet-area margin — so budget closer to 4 kg (9 lb). Always run mosaic separately from the wall field; mixing them into one calculation undercounts the floor badly.

At 1/8 in joint width. Unsanded grout has no silica grains — it is portland cement and pigments, smooth enough to tool into 1/16 in joints without scratching polish. Once the joint opens to 1/8 in or wider, unsanded grout shrinks and cracks because there is no aggregate to resist the cure shrinkage; sanded grout adds silica that both fills volume and controls shrinkage. Wall presets on this page sit at 1/16 in and use unsanded; floor and shower presets sit at 1/8 in and use sanded. If your wall joint is actually 1/8 in (rectified porcelain), switch to sanded even on a vertical.

The application is different, the math is not. On a floor you push grout diagonally across the joints with a rubber float, wait for it to firm up, then wipe with a damp sponge in circular passes. On a wall the sequence is the same, but gravity is against you — the grout sags in wide vertical joints before it sets, so you tool it twice (once to fill, once to compact after a 10-minute wait), and you never grout a wall in direct sun or warm breeze because the surface dries before the joint does. In a shower, wall field first, pan and curb last — the wet edge should never advance into fresh grout.

For wet areas, epoxy is the premium card — true 2-part epoxy is stainproof and rated for permanent immersion, which makes it the material of choice for a steam shower or a tub surround that sees daily soaking. But epoxy costs roughly 4× a cement grout per square foot and loses none of its working-time disadvantage on a wall. For a standard residential shower, a polymer-modified cement grout with a 15% margin is the usual answer; reserve epoxy for submerged tile (pan floor) or commercial wet rooms. The epoxy grout calculator page walks the full kit math if you go that route.