# Grout & Thinset Calculator > Free grout and thinset calculator: work out how much grout (kg and bags), thinset mortar, mixing water and cost you need for one tiled area — sanded or unsanded, with joint width and depth, all in your browser. Grout and thinset for one tiled area — bags, mixing water and cost, worked out entirely in your browser. - **HTML page:** https://siteometry.com/en/tools/grout-thinset-calculator - **Category:** [Decorating & Interiors](https://siteometry.com/en/tools/category/decorating-interiors) - **Figures live on the page:** tables, diagrams and worked figures the text refers to ("the table below") are drawn by the page and are not reproduced here. Each section below links to its anchor on the page. - **Runs in the browser:** Siteometry calculators need no account and send no input anywhere — every number below is computed on the visitor's own device. ## Grout and thinset calculator guide The calculator above turns one tiled area — a floor, a bathroom, a backsplash or a shower — into the consumables the job actually needs: grout (in kilograms and whole bags, with the leftover made visible), thinset or mortar (in bags), the mixing water for each, and an optional cost, in metric or imperial, all worked out in your browser. It is the consumables sibling of the tile calculator, which sizes the tiles and boxes. This guide explains how grout quantity comes from the joint geometry, how the trowel notch sets how far a bag of thinset stretches, why joint depth is an editable field here, and how back-buttering and mixing water fold in. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#grout-guide-intro_ ## How much grout do I need? Grout fills the joints between tiles, so the amount you need depends on four things: the tile size, the joint width, how deep the joint is filled, and the density of the grout. Smaller tiles and wider joints mean more joint length per square metre, so they burn through grout faster than big tiles with tight joints. The calculator computes the grout mass per square metre from the joint geometry, multiplies by the area, adds a waste allowance for mixing loss and sponge-off, then rounds up to whole bags and shows how much is left in the last bag so you can trust the round-up. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#how-much-grout_ ## Trowel notch and thinset coverage Thinset (thin-set mortar) is the adhesive bed the tiles sit on, and it is sold by how much area one bag covers. That coverage is set almost entirely by the trowel you spread it with: a bigger notch lays a thicker comb, so a bag covers far less floor. Bigger, flatter tiles need a bigger notch to bed fully, which is why coverage drops as tile size climbs. The calculator seeds a typical coverage figure from the notch you pick and keeps it editable — the exact number is printed on your bag and varies by brand, mix and how flat the substrate is. Use the table below as a starting point, and the samples show how the same area reads at different tile sizes. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#notch-coverage_ ## Grout per square metre by joint width Joint width is the single biggest lever on grout quantity. Doubling the joint width roughly doubles the grout, because the grout volume scales directly with the width of the channel it fills. The table below shows how the grout per square metre climbs with joint width for the calculator's default tile, filled to full depth. These figures come straight from the same formula the live calculator uses, so the table cannot drift from the tool — but change the tile size, depth or grout density and your own number will differ. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#grout-by-joint_ ## Joint depth and why this differs from the tile tool Grout does not always fill a tile's full body. The calculator defaults the joint depth to the tile thickness (grout filling edge to edge), but exposes depth as its own editable field — industry durability guidance asks for the joint to be filled to at least three-quarters of the tile thickness, so full thickness is the safe, generous default. This is the deliberate difference from the tile calculator, which hard-wires the joint depth to the tile thickness. Edit the depth down here — say a thick tile grouted only part-way — and this tool reports a smaller grout figure than the tile calculator would for the same tile and joint. Both are correct; they answer slightly different questions. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#joint-depth_ ## Mixing water and back-buttering Both grout and thinset are dry powders you mix with water on the day, so the calculator estimates the water from the computed powder mass — roughly a quarter of a litre per kilogram of thinset and about a sixth of a litre per kilogram of grout. These are planning figures shown with a ≈; the exact ratio is on the bag and depends on how stiff a mix you want. Back-buttering means troweling a thin coat of thinset onto the back of each tile as well as the floor, to guarantee full contact under large-format tiles. It adds roughly 15% to the thinset you use, so it is an optional toggle here — turn it on for big or heavy tiles and the thinset figure grows to match. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#water-and-back-butter_ ## Epoxy grout is different This calculator estimates cement-based grout, the common sanded and unsanded kinds sold as a dry powder. Epoxy grout is a different product — a resin and hardener with a much higher density and its own coverage figures — so these grout quantities do not apply to it. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#epoxy_ ## Frequently asked questions Short answers to the questions people most often ask about estimating grout and thinset with this calculator. ### How is the grout quantity calculated? Grout fills the joints, so the amount comes from the joint geometry: grout per square metre equals (tile length + width) ÷ (length × width) × joint width × joint depth × grout density. The calculator multiplies that by your area, adds a waste allowance, then rounds up to whole bags and shows the leftover in the last bag. ### Sanded or unsanded grout — which do I use? Unsanded grout suits narrow joints under about 3 mm (1/8 in) — walls, backsplashes and polished tiles that a sand filler would scratch. Sanded grout is for wider joints and floors, and is a little denser (about 1.76 vs 1.60 kg/L), so it needs slightly more per square metre. The calculator seeds the density from the type you pick and keeps it editable. ### Why does this give a different grout number than the tile calculator? The tile calculator hard-wires the joint depth to the tile thickness. This tool defaults to the same full-thickness fill but lets you edit the depth — durability guidance asks for at least three-quarters of the thickness. Reduce the depth here and the grout figure drops below what the tile tool reports for the same inputs; both are correct, they just answer different questions. ### Do I need to back-butter, and how much extra thinset is that? Back-buttering — spreading a thin coat of thinset on the back of each tile as well as the floor — is recommended for large-format and heavy tiles to guarantee full contact. It adds roughly 15% to the thinset you use. Turn on the back-butter toggle and the calculator grows the thinset figure to match. ### How much water do I mix with grout and thinset? As a planning figure, thinset takes about 0.25 litres of water per kilogram of powder and grout about 0.17 litres per kilogram, so the calculator scales the water from the computed masses and shows it with a ≈. The exact ratio is printed on the bag and depends on how stiff a mix you want — always follow it. ### Does this work for epoxy grout? No. This calculator estimates cement-based grout — the common sanded and unsanded powders. Epoxy grout is a resin-and-hardener product with a higher density and its own coverage figures, so use the epoxy manufacturer's chart for those quantities. ### Is anything I enter sent anywhere? No. The whole calculator runs in your browser — nothing you type leaves your device. You can export the shopping list to CSV or print it, both generated locally. _On the page: https://siteometry.com/en/tools/grout-thinset-calculator#faq_ ## Related calculators - [Paint Coverage & Cost Calculator](https://siteometry.com/en/tools/paint) - [Tile & Flooring Calculator](https://siteometry.com/en/tools/tile) - [Countertop Calculator — Slabs, Area & Cost](https://siteometry.com/en/tools/countertop-calculator) - [Carpet Calculator — Broadloom Yardage, Seams, Tiles & Stairs](https://siteometry.com/en/tools/carpet-calculator)