Grout fills the joint full-depth — the joint is a channel of width × depth × length

Grout fills the joint full-depth (ANSI A108.10), not just the surface — so the grout in a joint is a channel: width × depth × length. Depth equals tile thickness, which is why a thick floor tile uses far more grout than a thin mosaic at the same joint width.

A cross-section of two tiles set on a thin-set bed with grout filling the joint between them all the way to the bottom. Grout is not a surface bead: it fills the joint the full depth of the tile per ANSI A108.10, so the grout in any joint is a channel whose volume is joint width times joint depth times length. The joint depth equals the tile thickness, which is why the calculator asks for it. A side comparison shows that at the same joint width a 3/8-inch-thick floor tile holds three times the grout of a 1/8-inch-thick mosaic, because the deeper joint is a deeper channel. — Source: ANSI A108.10 §5.3.4 full-depth joint fill

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A cross-section of two tiles set on a thin-set bed with grout filling the joint between them all the way to the bottom. Grout is not a surface bead: it fills the joint the full depth of the tile per ANSI A108.10, so the grout in any joint is a channel whose volume is joint width times joint depth times length. The joint depth equals the tile thickness, which is why the calculator asks for it. A side comparison shows that at the same joint width a 3/8-inch-thick floor tile holds three times the grout of a 1/8-inch-thick mosaic, because the deeper joint is a deeper channel.

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    <img src="https://remodelcalculators.com/api/figure-embed/grout-joint-cross-section" alt="A cross-section of two tiles set on a thin-set bed with grout filling the joint between them all the way to the bottom. Grout is not a surface bead: it fills the joint the full depth of the tile per ANSI A108.10, so the grout in any joint is a channel whose volume is joint width times joint depth times length. The joint depth equals the tile thickness, which is why the calculator asks for it. A side comparison shows that at the same joint width a 3/8-inch-thick floor tile holds three times the grout of a 1/8-inch-thick mosaic, because the deeper joint is a deeper channel." width="800" height="460" style="width:100%;height:auto;border:0" loading="lazy">
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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/grout-joint-cross-section" target="_blank" rel="noopener">Grout fills the joint full-depth — the joint is a channel of width × depth × length</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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Grout Calculator

Calculate how much grout you need in bags, boxes, or epoxy units from your tile size, joint width, and area — TCNA/ANSI coverage formula. Free, no signup.

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