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Roughly Built

Tile

Grout Calculator

Figure how many boxes or bags of grout to buy for a tile job — tile size, joint width, joint depth, and product-specific coverage from manufacturer data sheets, with the math shown. Also called a tile grout calculator; same tool either way.

sq ft
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Defaults to tile thickness. Use less if thinset fills part of the joint.

%

Trade overage for cleanup and uneven joints — not a TDS constant. The 10% default is a labeled convention; add more for quarry tile.

Buy

1

25 lb bag

TEC AccuColor Premium Sanded

The working

Area 100 sq ft × (1 + 10% waste) = 110.0 sq ft

Tile 12″ × 12″ × 0.375″, joint 0.125″ wide × 0.375″ deep

Coverage (published chart): 364.5 sq ft per 25 lb bag

110.0 ÷ 364.5 → 1 25 lb bag (rounded up)

Joint volume, not floor area alone

Narrow joints on large tile drink far less product than mosaic with a wide joint. Manufacturers publish coverage as tables — tile size by joint width, for a stated bag or kit size — because density and packaging differ by product line. The honest estimate uses that product’s own chart when your size is listed, then adds waste.

Sanded cementitious, unsanded, and epoxy do not share a single coverage rate. Sanded mixes carry aggregate and are the usual floor pick for joints about ⅛″ and wider; unsanded is meant for narrow joints and soft stone that sand would scratch. Epoxy packs by the kit or gallon, not the same 25 lb bag math as a sanded cementitious line. Mixing tables across products is how people buy a bag that never matches the joint.

Chart cells first — formulas only inside a trusted zone

If your tile width, length, thickness, and joint width match a published cell, you get the published square feet per unit. Off-chart sizes use a joint-volume formula calibrated to that same chart, but only inside a zone where the fit stays tight — tiles about 3″ or larger on the short face and joints ⅜″ or narrower. Outside that zone you get a warning instead of a silent guess.

On the high-error cells we checked before shipping the formula path, the freeform estimate usually over-counts bags — it skews toward extra material, not short. MAPEI Keracolor S/U on mosaic and wide joints is a called-out exception that can under-estimate; the UI warning says so when that product and geometry combine. Joint depth on the charts usually equals tile thickness; if thinset fills the bottom of the joint, lower the depth and you will need less grout.

What we refuse to invent

LATICRETE SPECTRALOCK PRO Premium’s data sheet points to a separate coverage card and the Project Estimator. Without a stable official expanded table to cite the same way as the other presets, it stays omitted rather than scraped or guessed. Cementitious PERMACOLOR Select is included from LATICRETE’s published 10 lb chart.

Tile piece count is a different takeoff — run the tile calculator first, then come back here for joint fill. Grout sealer is a coating with its own coverage, not joint volume, so it is not folded into the bag count. The 10% waste default is a labeled trade convention for cleanup and whole packs; quarry tile often wants more.

Not affiliated with MAPEI, LATICRETE, TEC Specialty Products, or ARDEX. Coverage presets are drawn from each manufacturer’s own published technical data, cited below.

Sources

Frequently asked questions

How much grout do I need for 12x12 tile?

It depends on joint width, joint depth, and which product you buy — coverage is not the same across brands. For a common case, 12″ × 12″ × ⅜″ tile with a ⅛″ joint, a 25 lb bag of TEC AccuColor Premium Sanded covers about 365 sq ft per the manufacturer chart. Enter your area and product above for a bag count with waste.

What is the difference between sanded and unsanded grout?

Sanded grout has aggregate and is the usual pick for floor joints about ⅛″ and wider. Unsanded is smoother and meant for narrow joints (often ⅛″ and under) and for soft stone that sand would scratch. Joint width rules are on each product’s data sheet — this calculator’s presets follow those published ranges.

How do I calculate tile grout for epoxy vs cementitious?

Same geometry (tile size, joint width, depth, area), different packaging and coverage. Cementitious grout is usually sold by the bag (10 lb or 25 lb). Epoxy is sold by the kit or unit — MAPEI Kerapoxy CQ by the gallon, TEC AccuColor EFX by the 3 gal kit, ARDEX WA by the 8.8 lb unit. Pick the preset that matches what you will buy; do not mix coverage tables across products.

Why do MAPEI, LATICRETE, TEC, and ARDEX grout coverage charts disagree?

Each manufacturer measures yield for its own mix design and bag size. Sanded vs unsanded, polymer content, and epoxy filler all change how much joint a unit fills. That is why this tool keeps a separate published table per product instead of one generic rate.

How much waste should I add when buying grout?

Ten percent over the net figure is the usual allowance for cleanup, uneven joints, and the last incomplete bag. LATICRETE and others also suggest adding another 10–15% when grouting unglazed quarry tile. Waste is a trade rule of thumb, not a number from the coverage chart.

Does this include LATICRETE SPECTRALOCK?

Not yet. SPECTRALOCK PRO Premium’s data sheet points to a separate coverage card and the LATICRETE Project Estimator; we could not pull a stable official expanded table to cite, so it is left out rather than guessed. Cementitious PERMACOLOR Select is included from LATICRETE’s published 10 lb chart.