Grout Calculator
Enter your tiled area and pick a labeled grout coverage for your tile size and joint width — this calculator returns the pounds of grout and the number of 25-lb bags to buy.
Calculator
At a labeled 0.10 lb/sq ft, a 100 sq ft floor takes about 10.0 lb of grout — roughly 1 × 25-lb bag. Grout coverage depends on tile size, joint width and depth — coverage varies by brand, confirm on the bag.
Formula
Grout weight is the tiled area multiplied by a labeled coverage (pounds per square foot) for your tile size and joint width; bags round up:
grout_lb = area_sqft × grout_lb_per_sqft bags_25lb = ceil( grout_lb ÷ 25 )
The coverage figure is derived from tile geometry — smaller tiles and wider joints mean more linear feet of joint per square foot, so more grout. The derivation grout_lb/sq ft ≈ ((L + W) ÷ (L × W)) × joint_width × joint_depth × density is explained on the methodology page; here you pick the labeled coverage that matches your tile.
Worked example
Take a 100 sq ft floor of 12 × 12 in tile with a 1/4 in joint, which carries a labeled coverage of 0.10 lb/sq ft:
- Grout weight: 100 × 0.10 = 10 lb.
- Bags: 10 ÷ 25 = 0.4 → ceil = 1 × 25-lb bag.
So one 25-lb bag covers this floor with margin. Switch to 12 × 24 in tile with a 1/8 in joint (0.06 lb/sq ft) and the same floor drops to about 6 lb; go the other way to a 24 × 24 in tile with a 1/16 in joint (0.03 lb/sq ft) and it is about 3 lb.
Why grout coverage swings so much
Two floors of the same area can need very different amounts of grout, because grout fills the joints, not the field. The total length of joint per square foot rises as tiles get smaller, and the volume in each joint rises with both joint width and tile thickness (joint depth). That is why a mosaic sheet floor can use several times the grout of a large-format floor of the same size.
This calculator uses labeled planning coverages for three common tile-and-joint combinations rather than asking you to measure every variable, because bag yield already varies by brand, by grout type (sanded, unsanded, epoxy) and by how tightly you pack the joint. Sanded grout for wider floor joints yields differently from unsanded wall grout, and epoxy grout comes in fixed kit sizes rather than by the pound. Treat the result as a buy-quantity guide, not a precise fill volume.
Always confirm coverage on the actual bag for your tile size, joint width and grout type, and buy a little extra: a bag is cheap, a second trip mid-float is not, and a small reserve lets you touch up or regrout later. Mix only what you can use before it sets, and note that this is a material-quantity estimate — it is not a bid for a tile installer and not an installation procedure. For the joint width to pair with your tile, see the tile-spacing & grout-joint reference; for setting mortar under the tile, see the thinset calculator.
Frequently asked questions
How much grout do I need for 100 sq ft?
For 12 × 12 in tile with a 1/4 in joint (a labeled 0.10 lb/sq ft), about 10 lb — one 25-lb bag with room to spare. Larger tiles with tighter joints need less: a 12 × 24 tile with a 1/8 in joint is roughly 6 lb, and a 24 × 24 tile with a 1/16 in joint about 3 lb.
How many 25-lb bags of grout is that?
The tool divides the pounds by 25 and rounds up, so 10 lb is one bag. Because coverage varies by brand and by how tightly you pack the joint, buying one extra bag on a larger floor is cheap insurance against running short mid-float.
Why does smaller tile need more grout?
Smaller tiles pack more linear feet of joint into each square foot, and grout fills the joints. A mosaic floor can use several times the grout of a large-format floor of the same area, even at the same joint width.
Does joint width change the amount?
Yes. A wider joint holds more grout per linear foot, so widening the joint from 1/16 in to 1/4 in raises the pounds significantly. Joint depth (roughly the tile thickness) matters too — thicker tile means deeper joints and more grout.
Sanded or unsanded grout?
As a rule of thumb, sanded grout suits joints about 1/8 in and wider (most floors), unsanded suits narrow joints under 1/8 in (many walls and polished stone). This tool estimates quantity, not type — confirm the right grout and its coverage on the bag for your tile.