Grout Calculator

How the Grout Calculator Works

Grout volume depends on joint length per square foot, joint width, and joint depth. For a tile of length L and width W inches, the joint length per square foot is (L + W) / (L × W). Multiply that by the joint width and depth in inches, and by a density factor calibrated to cementitious grout, to get pounds per square foot. The calculator then multiplies by your area and adds a 10 percent waste factor. For a 12×12 inch tile with 1/8 inch joints at 1/4 inch depth, the result is roughly 0.19 lb per sq ft, or one 25 lb bag per ~130 sq ft.

Tile Size and Joint Width Matter Most

Small tiles have a lot of joint per area; large tiles have very little. Mosaic 1×1 inch tile has 96 inches of joint per square foot; 24×24 inch tile has just 8 inches. That is why subway tile and mosaics burn through grout while large format tile sips it. Joint width matters too — doubling the joint from 1/8 to 1/4 inch doubles the volume. Always match the joint width to the tile: rectified large format can take 1/16 inch, standard ceramic 1/8 inch, and natural stone or travertine up to 1/2 inch for a rustic look.

Sanded vs Unsanded Grout

Unsanded grout is cement plus polymer without aggregate. It shrinks less and is required for joints under 1/8 inch because sand grains would not fit. Use it for glass tile, polished marble, and narrow-set subway. Sanded grout adds silica sand to resist shrinkage and cracking in joints 1/8 inch and wider. It is the workhorse for floors, walls, and most residential tile. Coverage in pounds is nearly identical; the calculator handles both.

Tips for Accurate Estimating

Measure your actual job, then round up. A typical 25 lb bag mixes about 5 to 6 pounds of water per bag, so if you buy an extra bag, you can simply not mix it — unmixed grout stores for years in a sealed bag. Underestimating is worse: you risk running out mid-job, which leaves uneven color lines between old and new batches. For floors, always buy 1 extra bag beyond the calculator's result; for walls, the default 10 percent waste factor is sufficient.

Frequently Asked Questions

How many bags of grout for 200 sq ft?

For 12×12 tile with 1/8 inch joints, 2 bags of 25 lb grout. For 6×6 with 1/4 joints, 6 bags.

Does grout depth equal tile thickness?

Close to it. Most grout fills the full depth of the tile, so use your tile's actual thickness for the depth input.

What if the bag label says different coverage?

Bag labels are accurate — use them. The calculator is an independent cross-check and gives coverage within 10 percent of most brands.

Can I calculate epoxy grout the same way?

No. Epoxy is denser and comes in kits. Use the manufacturer's chart for epoxy products.

Do I need more grout for penny rounds or hex mosaic?

Yes, significantly. Small, round, or irregular tiles have much more joint length per area — double the result for conservative estimating.