Cement grout or epoxy?
The two products do the same job and are not remotely interchangeable as a purchase. At the same tile and the same joint, one covers more than twice the floor per unit — and reading the wrong chart is the commonest way to end up two units short on a Sunday.
The two charts, at a 1/8 in joint
| Tile | Cement, per 17 lb box | Epoxy, per 1 gal kit | 200 ft² takes |
|---|---|---|---|
| 2 x 2 in mosaic | 96 ft² | 56 ft² | 3 × 17 lb box or 4 × 1 US gal kit |
| 6 x 6 in | 266 ft² | 159 ft² | 1 × 17 lb box or 2 × 1 US gal kit |
| 12 x 12 in | 348 ft² | 156 ft² | 1 × 17 lb box or 2 × 1 US gal kit |
| 16 x 16 in | 462 ft² | 277 ft² | 1 × 17 lb box or 1 × 1 US gal kit |
Both columns are the manufacturers' own published figures — CUSTOM's Prism data sheet and MAPEI's for Kerapoxy CQ — read by the grout calculator rather than retyped here. Switch the product on that page and the whole chart switches with it, including which tile sizes and joint widths are on offer, because the two manufacturers do not publish the same ones.
Where the epoxy chart simply stops
The cement chart runs to a 1/2 in joint. The epoxy chart stops at 3/8 in, and that is not an omission — it is the widest joint that product is rated not to sag in. If your tile needs a wider joint than that, this particular epoxy is not a choice you are making.
The epoxy chart is also the more instructive of the two on thickness. It lists 4 × 8 in tile four separate times, at 1/2, 3/4, 1-1/8 and 1-3/8 in thick, and coverage falls from 139 ft² to 51 across those four rows. Same face size, same joint, nearly a factor of three in grout. That is the clearest published demonstration that what fills a joint is its depth, and it is the term almost every grout formula circulating online quietly drops.
Choosing between them, honestly
This is a specification question rather than an arithmetic one, so here is the short version and no more:
- Epoxy resists stains and chemicals, does not need sealing, and holds colour. It is bought for worktops, wet rooms, commercial floors and anywhere a cement joint would go grey.
- Cement is cheaper per square foot, far more forgiving to mix and to clean off, and does not have a pot life measured in the minutes before it stops moving.
- Neither is a substitute for a waterproofing membrane, whatever the box implies.
What this site can tell you with confidence is the quantity, from the chart the manufacturer published for the product you are actually buying. What it will not do is tell you which to buy — that depends on the room, and on how the floor gets cleaned.
Before the grout
The tile calculator gives the tile count with the pattern waste counted and hands the area straight to the grout calculator. If the floor is not a plain rectangle, the square footage calculator handles it first. Doing a whole room? The room materials calculator puts tile, grout and everything above them on one list.